>> and some of the lost irregularity is reinstated.
Anything "lost" in language cannot be reinstated. Lost irregularities in
particular can never be "reinstated", but can be recreated by analogies and
the like (the way English makes new irregularities with "thunk" "praught"
etc) but as such they bear no necessary relationship to the original
situation.
If they are "reinstated" they cannot have been lost.
Peter