I don’t see how a z offset would affect the top layer ? That was the original topic IIRC. But I’d like to understand. I mean I can see it screwing up the bottom layer but after that the print head is moving up at a constant interval layer height to the top. At the tip, any micron difference that happened in layer 1 would be long over.
This is correct for thermoplastics that fuse when squished together, such as PLA, as it will eventually iron itself out. However the clumpy thermoplastics such as ABS, TPU and PETG tend to stick to the layer beneath rather than fuse down into it as they work best when deposited not squished/fused. As such the excess is pushed to the sides, which then makes it’s way up when layed down in consecutive lines, such as the top surfaces. As the material can’t go sideways, so it’s forced upward. This causes the nozzle to drag through and pick up those clumps forced upward on the next layer above which results in blobs when it finally drips back off the nozzle as well as the scraping through the layer. I’m sure you’ll appreciate this mechanic leaves an unpleasant surface. Therefore with materials such as this it is imperitive to have the Z Offset correct as this sets the stage for the rest of the print moving upward.
Once I replaced the Z Offset machine start G-Code with that I posted in the Z Offset thread (with exactly the same height adjustment findings as 3DTech’s post incidentally), PETG and ABS now come out pretty flawless (assuming you know the material well enough to have dailed in the rest of the profile also, such as flow rate, temperature and cooling). My results show all surfaces, bottom, top and somewhere inbetween are like untarnished glass. Well, 99% of the time, these materials are still clumpy. This principle I imagine being the same understanding 3DTech was getting at in this post noted above originally, hence the need to adjust the Z Offset.
However, there is good reason BL squish things down well. Bed adhesion. I can imagine their stance being it is better to have good bed adhesion and slightly marred surfaces, than have a model pop off and destroy the hot end. So the caveat here is please be aware of your materials bed adhesion preperties and take appropriate measures to ensure it remains stuck to the bed during printing if you are going to adjust the Z Offset upwards for that material. That said I have had no adhesion issues to date.
Anyway, this is just from my experience over many years now with 3D prinitng (building printers from scratch, upgrading cheap printers, contributing to the Marlin source code and writing out many profiles for Klipper) during which time I have done extensive work on Z Offsets as these principles apply to all printers. I hope it helps some folks.
As an aside to the above, somebody in another thread uncovered a very well written and informed article;
PETG Ultimate Filament Printing Guide [2022]
I say well informed as with almost every “issue” the article covers, from blobs and zits on the print, stringing and poor surface quality, they recommend looking at the Z Offset in the first instance. This is for each and every issue quoted and I think this serves as a really good guide for printing with PETG.
What I will do is post a Benchy on Makerworld with all my profiles for Printer Profile, Printing Profile and example Filament Profiles included for perusal, copying or just keeping. I’ll post a link here once completed as I have a few more tweaks left to do.
It’s just unfortunate we don’t have facilities on BL printers that have been available on each and every single 3D Printer made over the past 7+ years to adjust the Z Offset height, both programatically and as a “live” option whilst printing. BL have brought some incredible advanced hardware to the scene, which is evident in it’s use and popularity for “just working”. However, there are some issues remaining with software; including firmware, G-Code (please let use use variables in G-Code like “#My_var_name = 1; if #My_var_name == 1; do_something etc” and also please BL document all your G-Code commands and features the firmware can use so advanced users can squeeze the most out of this hardware!) and slicer (looking at your Bambu Studio), that really need addressing at some point. But uintil then I guess community workarounds will be commonplace. I guess this is keeping the spirit of the 3D Printing community alive at it’s core - input from the hive mind 
Seems like there have been enough replies in other threads about the left nozzle failing calibrations or the offset calibration sensors having issues with the left nozzle that it may warrant being added.
You aren’t alone, this is still an issue in October. I had a partial clog earlier today, did a couple cold pulls with PLA to clean it up, ever since the printer has been trying to load PA6 at 215C, with predictable results. After trying everything I could think of to get the printer to treat PA6 as PA6, not PLA, I opened a support ticket, sent logs, and started a factory reset in hopes that’d make the printer usable again.
In my experience, if you initiate the loading sequence through Bambu studio instead of the touch screen, it should work as normal.
Maybe I’m having a different issue. I’m getting the same experience loading through Bambu Studio as through the touch screen, and with jobs sliced & printed from BS, it tries the load at temperatures far too low and fails. Sadly, the problem did persist across the factory reset. Hopefully support comes up with a solution soon.
after the last slicer’s update there are a lot of broken things like
you send the file to the printer, software suddenly give the pop up to sync the device. you click “later” and the window pops up again and again without letting me close the program
also the device doesnt connect if you dont click on device tab after you load the program.
then u click “device” and printer takes seconds to connect. ridiculous.
Yeah the last thing you are saying its happening also to me
Slicer?
It is obvious that is due the last update. Plain and bright. I have all the ruined prints for you to see the time wasted.
edit: they gave updates today. did not try yet but I have one last bit of “hope”