Comment by izacus

I don't quite understand what you're arguing here.

I'm merely saying that the root cause was misidentified - the performance degradation didn't happen due to fragmentation, but because the flash storage was degraded to the point where the write performance dropped significantly. This happens faster for eMMC vs. SSD-style storage.

Copying the DB file moved the data to different storage blocks which is why it (temporarily again) improved performance.