Does make sense to check the profile files now that you said it, kek.
Found the exact lines you quoted and to me it looks like the "currentSalesSum" is the money exchanged in trades with the SCAVCAT trader, I made a new profile and compared the lines.
For some reason the "currentLevel" was set to 0, I think tarkov went full confusion and set the value to "null" because of that.
Thank you very much for your help kind person from the internet,
Glhf in your future raids!