This is an IMPORTANT ANNOUNCEMENT concerning GEOID18 and SurvCE.
The NGS published a bad GEOID18 implementation on their website earlier this year. The error was discovered / announced yeseterday Monday 9 December 2019.
Many / most vendors utilized the errant GEOID files posted on the NGS site to build their GEOID files, including Carlson Software.
I have verified that the GEOID 18 file distributed with SurvCE Version 6 contains the errant grid points (about 1 in 500 points is incorrect, with a 6 cm maximum error.)
This PDF shows how to check if you are using the errant GEOID in SurvCE:
I believe that your best course of action is to revert to GEOID12B at this point.
Carlson will release an updated GEOID soon, however it may be difficult to jump on this wagon again.