Same query - different results between two reports

Hey Guys,

I was posting a thread on this last week but dunno where it disappeared (or maybe I didn't submit it...) 🤔

Anyways, to the point: I have a strange issue with my reports. I made two versions of one report connected to the exact same datasource but I'm getting slightly different data in them... 
In first one:

And in the second:

All filters are cleared, relationships are exactly the same. I don't know how/if it matters but there are two queries from one source - first one is being unpivoted into other, where the data is being pulled to the report (queries are exactly the same).
Unfortunately I cannot share the data with you as it's strictly confidential (and intranet), and preparing sample data for such amount of entries would take some time.

I ran out of ideas what may cause the issue... Anyone have any idea?

Thanks in advance for any help