[1.0] Modifier clicks broken

[bmiww]

Hello!

Been playing a heavily modded world for a while - also have been turning some mods on, just to turn them off moments later, so could be a source of unstability.
Playing in multiplayer.
Anywho - at some point one of us has done something in the map - and for both of us - We can no longer use any of the modifier actions (shift or ctrl) for bulk moving items and all the useful quick actions. Blueprint deletion also has stopped working.
In older saves, it still works, but quite some time has passed + We would like to determine what exactly caused this in the first place.

As per forum rules.
Possible things that were being done before the breakage was noticed:
My colleague was setting inventory filters. Was performing automatic module replacement via the Module Inserter mod.
I was using a mod for downscaling circuit networks - using a tool to grow/shrink a blueprint of combinators.

Any debug guidelines, possible fix ideas?

Anywho - We ended up agreeing to a rollback - but still a weird break - will pop a new report if We bug off again.
Sorry to the mods if this ends up being spammy. But if anyone has any ideas regardless, much appreciated!