Counter and elementary logic gates
There is a note about this in the original RCA (now TI) datasheet:

OR, Your problem occurs in the transition between 10 and 09, when there is valid CO activity for both counters.  It could be that in the Proteus model, one CO is going low before the other has a chance to return high, a race condition.

Either way, very small R-C networks between the CO outputs and the NOR gate will filter this glitch.  I would start with a 1 us time constant, like 100 ohms and 10 nF.