Leshiy leak

Tried the search function but haven’t found this particular leak discussed.

My leshiy classic e gauge failed so I switched it out w a wika gauge along w the o-ring inside but when I go to fill it it leaks.

The leak seems to be coming from the grub screw that holds fill cover in place and I didn’t even touch that screw other than to screw it in to remove the fill cover but never unscrewed it completely. Anybody deal with this before and any solutions?