(Note this is about LibreOffice Online, observed in it's Collabora CODE incarnation, and not about the desktop office suite!)

In Collabora CODE (at least versions 4.0.x and 4.2.x, but probably also 3.4.x), in Calc sheets the row headers and the cell selection marker rectangle often get "out of sync" with the actual table contents.

This means (some of) the e.g. row headers have different heights than the actual rows in the Calc table, causing a mismatch between headers and table and making editing - especially selecting the right cell for editing - basically impossible.

The only solution is to exit the editing session and rejoin, which is very inconvenient - especially as the session has a high likelyhood to get out of sync again soon.

I could not reliably find a trigger to reproduce it, but it unfortunately still happens pretty frequently. Observation seems to indicate that it might happen more often (or even be caused by) concurrent editing of several users in the table.

So far, I had always hoped that it would finally be solved in the next bugfix release, but the problem even survived multiple "bigger" version steps so far without major improvements in this regard. :-(