We've done some additional testing on 3ds Max 2018.4, FP 5.4.1 & V-Ray 3.60.04, but as mentioned previously, we can't reproduce it. As up to now, we don't have this unwanted behavior reported by any other user, another plug-in(s) or script(s) might interfere.
Would you mind to specify, which other plug-ins and scripts are you using?
Please feel free to perform a fresh 3ds Max install just with our plug-in to check if there's any difference.
Once again, big thanks for your collaboration, your feedback is very important to us.