this is strange problem. im still learning about this stuff, but since i been messing with flippers abit and reading abit well here is why coils can overheat.
basically a coil has a high power side, that gives the "power" to the coil, but also has a lower power side. now on non fliptronics games the end of stroke is really important, cause it will be there to put on the lower power. like i had a problem of a weak flipper on the left on a party zone, so i just adjusted the end of stroke to come on almost at the end and it solved the issue.
on creature u have fliptronics board, so even if u cut out the end of stroke switches the coil wont stay up cause the low power side wont kick on and the board would make it cut out after like a few seconds.

but anyways right from the master himself clay. hopefully he wont mind me posting this, but hey full credit to him.

On WPC fliptronics and later games, if there is a marginal flipper switch reading, this causes the high powered side of the flipper to rapidly oscillate between on and off. The holding side of the flipper coil never engages. This problem will cause the flipper coil to get very hot in a short time. First try cleaning the flipper board optics. If this doesn't work, the LM339's on the Fliptronics board at U4 and/or U6 (or CPU board on WPC-95 at U25 and/or U26) will need to be replaced.
or
Bad regulation of the 12 volt power to the optos can cause the flipper coils to get hot too. Though rare, the 7812 voltage regulator on the power driver board could be failing, or the electrolytic filter capacitor for the 12 volts.