My H2S has issue with layer shift since yestarday and its getting worse..I have almost 1700h print time, last maintenance I did 2 weeks ago. Its worse along Y Axis than X. It doesnt seem to be affected by Z axis.
you said retighten the best tensioners. Did you actually do the calibration of the tensioners (loosen move back and forth etc)? Mention it just in case.
A lot of the layer lines seem to come from different layer times.
Try to print a tall cylinder or block and see if it has the same issues.
I have the feeling that its topology based.
Exactly as mentioned in Wiki.
I’ve print few mocks almost 1kg each, perfect rectangle at base, 8% infill adaptive cubic
Last print compared to previous. Wall paraller to X Axis prints flawessly this time. I don’t see any patern. It looks like there is some loose that shift layers from left to right… since position rely on stepper motors and shifts are within some margin my guess is caused by extruder itself
There’s your problem.
This is the weakest point of these machines since they started using the same nozzles as the A1 and A1 Mini.
And i say that because every 2 to 3 months i have to take of the nozzle from my A1 Mini, remove the supporting part behind the nozzle so that i could tighten those damn screws.
But at least it’s an easy problem to solve 
for me it tooks 4 months and almost 1700h printing time and >50kg of filament (including few fckps where nozzle hits hard) . At least I have ultra strength loctite 272 and hope I wouldn’t need to remove them any time soon 
Trust me, they will need to be tightened again. Be careful with the Loctite because the part where the screws go in strips very easily and i don’t know if those parts are in the store as replacements.
Anyway, i am glad you solved it and it’s a resolution for users in the future in case they also have the same problem 
Take those 3 loose screws all the way off, and check the 4 screws on the underside [not visible from exterior]. If the front 3 were loose, the back 4 might be falling out. I tighten these every ~3months on my A1s which use a similar nozzle holster architecture
I’ve check them also. They were tight
I’m using 272 in harsh environments and it works great. Like well known issue with loosening header bolts in ford’s 5.0 ■■ - it helped in my case and I never need to retight them again 
Thanks for the tip. Maybe i’ll try it next time they need tightening 
