I honestly don't know what is causing this, but I'm pretty certain it has to do with traveling between DLCs, on a hunch. Last Monsoon season, puddles formed as usual. I sandbagged the ones near my base. Dry Season came along and I expected them to recede and disappear. The ones I sandbagged did, but the others only receded to a point. Then during Mild Season, they started expanding again (it was raining during this), and eventually they starting receding again, before disappearing fully. Now it is Hurricane Season and the previous disappeared puddles are randomly expanding again (it was not raining during this). These are not new puddles forming, they are puddles from last Monsoon Season coming back from the dead, seemingly ones that I did not kill with Sandbags.
Steps to Reproduce
No idea. I'm in a merged RoG-SW-HAM world and puddles started acting strangely after Monsoon season ended, I suspect because of DLC travel.
This issue has not been confirmed by a developer yet.