sterretje:
You're using delay; so only the next iteration of loop (e.g. after 2 seconds) will react on a changed count count.No idea why the L298 causes an additional spike (electronics is not my strong point).
By the way, if you use a solution based on blink without delay you don't need interrupts. This is actually an example where they are not needed and don't give you the desired result.
Right, yeah I figured there would be a better method to accomplish the functionality, unfortunately this current issue has to be resolved before any of that matters though.