# After v1.15 → v1.20 upgrade, Apply Tension always fails — bottom-belt deviation ~40mm **URL:** \ **Category:** Troubleshooting\ **Created:** [May 3, 2026, 2:39am UTC](https://forums.maslowcnc.com/t/after-v1-15-v1-20-upgrade-apply-tension-always-fails-bottom-belt-deviation-40mm/25745 "2026-05-03T02:39:43Z")\ **Posts on this page:** 1\ **Showing post:** 24
**Author:** ![bar](https://yyz1.discourse-cdn.com/flex031/user_avatar/forums.maslowcnc.com/bar/32/10_2.png) [@bar](https://forums.maslowcnc.com/u/bar)\ **Post date:** [June 17, 2026, 12:19am UTC](https://forums.maslowcnc.com/t/after-v1-15-v1-20-upgrade-apply-tension-always-fails-bottom-belt-deviation-40mm/25745/24 "2026-06-17T00:19:44Z")
1.22 is going to have a pretty major rewrite of how all of that works which might fix this issue. Do you see the same behavior on this version: > [@Interstitial Firmware Releases](https://forums.maslowcnc.com/t/interstitial-firmware-releases/20215/918): > > Latest Test versions 2026/06/09 [index.html.gz](https://forums.maslowcnc.com/uploads/short-url/wqK3C41xHEeb4LIfl21GkLi6ot4.gz) (146.4 KB) [firmware.bin](https://forums.maslowcnc.com/uploads/short-url/yNHqRDBdCqlaKHikwK1glCFSJi6.bin) (1.9 MB) Updates since V1.21; Sanity check startup Z with non-reset warning for high Zm Retry LM solver with perturbed anchors FluidNC Config Items: show active Config/Filename instead of hardcoded maslow feat: OTA “Check for Updates” with configurable release stream Render live Find Anchors path trace from calibration waypoints Update startup Z/Z-home handling, persist Z-stop home across restart Find Anchors: switch canv… --- _[View the full topic](https://forums.maslowcnc.com/t/after-v1-15-v1-20-upgrade-apply-tension-always-fails-bottom-belt-deviation-40mm/25745)._