Exhaust end cap screws

So I've had my '11 for about a year now and so far, so good. I've put on about 6300 miles. No problems.
Been feeling pretty smug that nothing has broken or fallen off. Until now.
I went to the local Guzzi shop to buy some oil. There I met a couple of guys passing through on their BMW GS 1200s.
One of the guys was admiring my Tenni and happened to notice a missing screw on the exhaust can's end cap.
I happen to know it was there that morning but not now.
The MG parts manual does not describe the screw size (PN 981143) but matching them at the hardware store revealed the remaining two screws were both 6x20 mm SS hex cap screws. I bought and installed the three new ones and kept the old two as spares.
I went for a ride last night and discovered this morning that a screw is gone from the same position as the first screw. The one farthest out from the tire.
WTH? I retrieved one of the old screws and after applying some high temp Loctite 246 I installed it. This isn't enough to force the sale of my Tenni but this is interesting. Any one encounter this? I'm curious if the GRiSO hive has knowledge of the actual screw length? Maybe my screws aren't original and they are too long? There are plenty of threads in the exhaust pipe and 20mm length doesn't seem necessary.
Maybe I'll try a small lock washer under each head to make sure but it has been working for almost nine years until now.
There are worse problems to have.

Tvboy,

I have a 2014 that I bought new 5 years ago. About 6 months ago I noticed one of those screws missing from the lower exhaust end cap. Don’t know how long it had been that way. I bought a couple from AF1 and installed the new one with blue lock tight. It’s been fine ever since.

I regularly check mine. Even then, sometimes one goes missing.

Thanks for the replies.
I checked mine again this morning and the one I had Loctited was still there but the upper right screw was gone now.
I've replace the missing screw and applied Loctite to all three now so we'll see what happens.
It's so odd they've chosen now to start vibrating out.

I'm sort of glad mine aren't the only ones.

Moving onward.

Lost all 3 of mine. One at a time of course.

Luckily had some spare SS bolts lying around. Think I used red Loctite on them when I put them in.

Y'all realize, heat releases loc-tite....... Try skipping it and slip a bit of mono-filament fishing line in along the screw. It's what old farmers do when they don't have Loc-Tite.

I've heared about the fishing line trick but never thought it would work.

I'm using high temp Loctite so we'll see what happens.