Conversion completions error after adding secondary dimension to reports

I have been clicking around analytics and saw that the following problem: When adding a secondary dimension to reports (both custom and dashboard), sometimes the conversion numbers (goal completions) will get messed up. By “messed up”, I mean certain numbers, for example 8, will be repeated in a way that makes no sense.

• The main problem here is that the error is not coming from any specific account, dimension, report or combination of these.
• I tried to find a pattern regarding in which instances this is occurring (e.g. when combining device category and campaign in a locations report), but it all seems very random to me.
• The only consistency that I can spot is that the error only shows on the completed conversions column (all steps).

Furthermore, there is another interesting insight:

• This error starts appearing when taking a time frame of longer than 60 days
  • Sept 3rd – Nov 3rd; conversion completions jump from 0 to 1 – so I’m assuming (only) the data for this period is correct
  • Sept 1st – Nov 3rd; conversion completions jump from 0 to 2
  • July 1st – Nov 3rd; conversion completions jump from 0 to 3
  • Jan 1st – Nov 3rd; conversion completions jump from 0 to 8
  • And so on….

In this case, I looked at these two reports and got these same results highlighted above:

1. Audience < Geo < Location Report; primary dimension “Country”, secondary dimension “Campaign”, filtered by de_diving.
2. Acquisition < Google Ads < Keywords; primary dimension “Keyword, secondary dimension “Criteria ID”, no filter.

I appreciate any help i can get on this since I am completely in the dark here. Thanks!