Map updates when returning to area mapped minutes ago

I was mapping out a swamp and when I returned to an area I had already mapped out, the colors on the map began changing and becoming 2-3 pixel wide lines of different colors resembling what was there. Some parts of the mapped area were regenerated in 1.18, if that may be of any use.  I have attached a picture of the 1.18 chunk regeneration thing, but the video of the actual map glitching won’t upload (over 10 mb)

Steps to reproduce: 

1. upgrade a map to level 2/4
2. fill up that map (try to do so In a swamp as this is where I observed this happening)
3. go away from a section then return to it.

Expected results: nothing happens and you have a full map now

experienced results: the map will change and somewhat jagged lines will appear