0. Modloader: Fabric, Mod Version: fabric-1.20.1-9.1.10

1. Describe the bug
   After updating the mod today the backpack contents are gone.

2. Write steps to reproduce the bug

• use the mod version from a few days ago (before the crafting table got moved) and fill a backpack
• update the mod
• observe how the backpack is empty

3. What is expected behavior
   The mod update does not reset backpack contents

4. Screenshots (If applicable)
   

I also had this issue, and it happened because I clicked "Check for Updates" on prism launcher. If it were me, I would remove the update from Modrinth and CurseForge until this bug is fixed, because as far as I know there is no way to filter out beta versions of mods in the launcher:
https://www.reddit.com/r/PrismLauncher/comments/13ia9v2/only_download_stable_versions_of_mods/

Until that feature gets added and enabled by default, releasing betas should probably be restricted to places that aren't automatically downloaded by popular launchers. Just my 2 cents.

I also had this issue, and it happened because I clicked "Check for Updates" on prism launcher. If it were me, I would remove the update from Modrinth and CurseForge until this bug is fixed, because as far as I know there is no way to filter out beta versions of mods in the launcher: https://www.reddit.com/r/PrismLauncher/comments/13ia9v2/only_download_stable_versions_of_mods/

Until that feature gets added and enabled by default, releasing betas should probably be restricted to places that aren't automatically downloaded by popular launchers. Just my 2 cents.

do you play on server?

This issue is not resolved and should be addressed.
The mod version is the same on our client and server, and the backpack contents are gone.

What files should be restored from the backup of the world?

do you use trinkets integration

Yes we do have the Trinkets mod as well.

Join my discord so we can investigate the issue
write the message in bug-report

do you play on server?

Yes, I maintain it

do you play on server?

Yes, I maintain it

can you join my discord and write a message on bug report so we can investigate

My server is using EasyAuth, (from my limited testing) this bug seems to affect only players that are logging in using local offline authentication and not Mojang online authentication.

Did you update mod on server
Update is marked as a beta and you should make backup of your world before updating the mod to beta version

@Tiviacz1337 how is this resolved? items in the backpack and inventory still disappear when just moving stuff

anyone here is able to test with the mod I'll send via dm?

Did you update mod on server Update is marked as a beta and you should make backup of your world before updating the mod to beta version

Yes, I updated the mod on the server, actually it got updated automatically by packwiz, I have backups, but they were not needed as I noticed that all the backpacks simply got regenerated in a sense (they got a new BACKPACKUUID), the previously owned backpacks still existed within the respective player folders in world/backpacks.

As a fix I gave back players their last UUID backpack (sort by last change in the respective world/backpacks/PLAYER_UUID folder) using /tb restore PLAYER_NAME BACKPACK_UUID command, though I suppose (while the server is offline) you could also simply copy the name of the lastest created BACKPACK_UUID, delete it and rename the second last (now the latest as you just deleted the previously latest) to the copied BACKPACK_UUID (I have not tested this approach though).

anyone here is able to test with the mod I'll send via dm?

I can do it in a few hours most likely, I'm messaging you on Discord.

Did you update mod on server Update is marked as a beta and you should make backup of your world before updating the mod to beta version

Yes, I updated the mod on the server, actually it got updated automatically by packwiz, I have backups, but they were not needed as I noticed that all the backpacks simply got regenerated in a sense (they got a new BACKPACKUUID), the previously owned backpacks still existed within the respective player folders in world/backpacks.

As a fix I gave back players their last UUID backpack (sort by last change in the respective world/backpacks/PLAYER_UUID folder) using /tb restore PLAYER_NAME BACKPACK_UUID command, though I suppose (while the server is offline) you could also simply copy the name of the lastest created BACKPACK_UUID, delete it and rename the second last (now the latest as you just deleted the previously latest) to the copied BACKPACK_UUID (I have not tested this approach though).

what if it is a singleplayer instance/world?

we found the bug it works on sever and singleplayer update will be available tomorrow

https://www.curseforge.com/minecraft/mc-mods/travelers-backpack-fabric/files/all?page=1&pageSize=20 fixed