74hc14 problem

[david_c_partridge]

Multisim 10.1.1 is behaving a bit oddly.  The 74HC14 in the attached circuit works for a while and then at about 7mS into the simulation, it stops switching when the input switches, and some time later it decides to work again.

If I replace the 74HC14 with a 74HC04 the circuit works??????

[david_c_partridge]

Am I on someone's black list?  No-one seems to want to look at this 😞