I get funny LVS errors when using rnwell pcells from my pdk:

ntap connected to GROUND !
(some of my nwell resistors terminate at gnd)

floating nxwell is not allowed
(I see this for series segments of my R that are not the top/bottom segments)

I tried applying the HOTWL layer but still see these errors.

The error message in your case seems to be an ERC error. The check "ntap connected to gnd" should normally be performed on any nwell that contains a p-mosfet" or an nwell forming an isolation ring of some sort. This check should be done to ensure no nwell/p-sub diode is forward biased.

The resistor nwell should be precluded from this check. You could solve this issue by examining the generation of the "nwell" layer used to perform the ERC check.

Modifying the generation of the nwell may stop these violations on the resistor nwell.

Hope this helps.