Ubuntu 18+Erpnext v12 local changes in app "frappe" that are not committed

I am on Ubuntu 18, Erpnext v12.2.2, frappe v12.0.20
Since few days, I can’t make “bench update” with no issue. A the end of the command, I 've got the message “local changes in app “frappe” that are not committed.” and my website remain unusable presenting an update warning status message box.
I found many subject in this forum dealing with these problem and I made all the git command recommended with no effect.
Even if I proceed with a fresh install, a bench update lead to this failure.
The only way to get my installation working again is to do bench update --reset.
My question is : what are the consequences if I do only bench update --reset in the future, because I can-t fix the problem?

I 've got the message “local changes in app “frappe” that are not committed.”

Simply means that you’re manually changing the code on the server or it is being changed.

bench update --reset simply reverts those temporary changes when updating the system. You may want to check what changes are being made by going to the frappe app folder and running git status

Thanks for your reply,
when I 'm running git status, I ve got the following message :
"On branch version-12
Your branch is up to date with ‘upstream/version-12’.
Changes not staged for commit:
(use “git add …” to update what will be committed)
(use “git checkout – …” to discard changes in working directory)

    modified:   yarn.lock

no changes added to commit (use “git add” and/or “git commit -a”)"

It’s happened on a fresh install (easy install script on github).
So if I understand, if I use bench update --reset, my website work again but will never be updated with a new version?

Is there a solution ?

Yes. I got that error too.

 bench update --reset 

is the way to go.

The option --reset means that if you made any local changes in your frappe or erpnext code at the developer mode, these will be wiped off. In fact, this may be what you want - total assurance that the code files in your local system that matter are exactly like the frappe / erpnext repository.

(I think you don’t need to be concerned with this at this stage.) To preserve the local changes, the changes may be stashed before doing bench update --reset, and put back again.

Many thanks Joseph, I will wait for somebody make the correction.