Is it possible to use LED lamps in ceiling r80 eyeball fittings
18 Watts is a lot for LED, so not surprising for it to be warm.  

Sometimes LEDs have a slightly larger diameter and this may not allow them to screw in 100%, but this doesn't seem to be the case for you.  

One suggestion is to take a flash light and examine the socket of the fixture for any evidence of arching.  Look for black or burnt streaks. The slightest damage to the socket could cause new bulbs to fail unexpectedly.