I dunno about the manual safety variant, but there are at least two known problems with the civilian version.
One is the known drop fire problem mentioned in this thread. Several slow motion recordings have shown that a factor in this issue is that the trigger has enough inertia to essentially "pull itself" when dropped at the right angle, due to the lack of trigger safety. Unless the trigger is substantially different in weight or construction in the MHS version, I can think of no reason why this issue would not be present if the manual safety was disengaged, but it seems reasonable that engaging the manual safety would prevent this problem. However, this does not mean the guns is safe with the manual safety, as the second issue shows.
The other is a lesser known issue that presents itself in a fashion much like the above, but is mechanically different in nature. If the back of the slide where the striker assembly is exposed is struck with enough force, the striker may (but will not always) fire as though the trigger has been pulled. I can't say whether this problem would be present with or without the manual safety being engaged, especially depending on any internal differences between manual safety or no manual safety. This issue is not something where you have to smack the gun with a sledge hammer. It was induced using a plastic gunsmiths mallet.
http://www.thefirearmblog.com/blog/2...st-scientific/
The above is not isolated, I've seen another test of the same issue occurring.
The only common theme between the two is that smacking or dropping the gun on the back of the slide/frame is bad news. I'm not a fan of the trigger tab safeties, but that or a lighter (literally weight of the mechanical component) trigger would fix the first issue. The second.... Who knows. Could be multiple issues all at once.