Broken (previously working) workflow shows as active and successful

Hi everyone,
I have a quite long automation workflow that is not working properly but is still marked as active. Even if trying the manual run and watching it state “success”. It is behaving erratically and some parts work while others no (that were working before).

I think something may be wrong at a deeper level.

I built a quite long automation workflow that works on creation for a record. Everything was working as I were adding steps until I added the last steps. At that point the workflow was simply throwing an error that was blank (the error was disappearing simply deactivating the last steps). As a solution, I then extracted the last part and put it in a separated workflow. The detached part seems to work but the main part is not behaving properly. Only a very small part is working (the very first actions of every subpart).

It seems as if at some point something broke and even if there is no sign of it (active and successful runs), the workflow is broken. Maybe the root cause is this blank error I was getting previously.

The run history doesn’t show any problem or throttling.

Some additional questions:

What is the maximum (or recommended) number of actions in an automation workflow?

What does a blank error means?

By the way, as a general question, would you recommend to have a long unique workflow or several smaller ones?

Thanks a lot.