Well, I did a lot of changes in our part setup and so.
First thing we had a SQL database error, where data was not truncated I think (not my field). That sped up the whole MRP process from 12+ hours to 66 minutes.
Additionally I trimmed down lot sizing days and short horizon planning to reduce the job suggestions from 25000 to 5000ish. Generally I used on lot sizing days of supply 30 and 30 days also for short term horizon.
We have a business need to see finite scheduling for all resources minimum 360 days, which is possible because we have really total 20 manufactured parts with around 400 components total. Some products have 9 levels, but only like 1-2 per quarter.
Also, a lot of resources were added without calendars and finite days. We had also people / operators as resources. One shift leader uploaded new operators without calendars and that caused delays in MRP process also or more like lag.
I did check all the steps here which helped to understand several bad parameters that were hiding in the system: Finite Global Scheduling Will Not Complete - #19 by GPareja