Bug on excel online version - locked cells

Hello,

Let's explain the situation:

In my company, we have office365 and many people don't have the extended access (so they can't use the desktop version of excel word etc, they can only open and work on files online).

Since a few days, when using an excel file that has locked cells, they get the message as if all cells are locked si they can't work on those files at all.

Using the same files in the desktop version works well (locked cells are locked, and unlocked cells are unlocked) and using those files by someone who has the extended version works also well.

Any idea what to do? Please... I've not idea what's going on, and how to solve this...