93 civic cx transmission

Hi all, I have a 93 civic cx hatch, 180000km, but every time I decelerate
from a speed above 40-60km/h, it will always jerk between the switch of
gears from 3ird to 2nd at about 30km/h. Whether I decelerate very very
slowly or almost slam the brakes, once it's at about 30km/h it will always
jerk.

Also, if going lets say about 60km/h, than put car in neutral, wait a second
or 2, and re-engage into the Drive position, it will jerk and put itself
into 3ird and then into 4th which is overdrive i think. So why does it not
go into
4th so that it's smoother, than downshift into 3ird should more power be
needed.
All cars I know will always keep the higher gear unless power is needed.

I tried al sorts of tranny oil additives. no change. Did a full tranny fluid
+ filter change, still no change.
Could it be a solenoid or something.
Speeding up across the gears seems all fine.
any ideas????