Sounds like he might have allowed the lip of the seal to roll over when installing the seal(s) or installed them dry. The spring on the back side can slip off if the lip rolls over on installation making them prone to leaking. Installing them dry can cause them to "hang up" on their shaft upon startup and damage them as well.
I doubt a clogged flametrap or oil seperator would become apparent only after servicing the seals. I am only guessing but something must be amiss with the seals.
I guess it could be the gasket if in fact he removed the cover to replace the seals.
Randy
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