IIrc, there are certain actions that temporarily lower your rep. And it's not shown to you in the UI (Dev doesn't believe in 'spoon-feeding' people.)
Most of them are things you'd expect to be 'frowned upon'.
Try checking your phone a bit more often. Like right after you do something you suspect might lower rep. So you spot what it was that gave you the temporary 'debuff'.
Also keep in mind that some stats don't update 'in real time'. They happen once a game day (at either 00:00 or 01:00, IIrc).
With as many variables as this game has, that's just way too many checks to be preformed at every action. It'd bog down most any 'puter