I had the base lookin great. Then I applied the first coat of clear and went outside for a minute. When I went back in, it was sagging and dripping. I checked the room temp and found that it had dropped to 59 so I waited for the temp to come back up to 70 and applied 2 more coats and no further sagging problems. Please tell me what is the best way to fix it?

Good luck.I'd block it out and start over!

Wet sand and buff. a small block over the sags and some light sanding will save the job.