harley lights burning out

i have a 2015 harley davidson breakout, and in the year and a half i've had it, i've replaced WAY too many brake lights.

the rear turn signals are 1157 bulbs, so do running lights, brake and turn. the rear right bulb burnt out about a month after I bought it, but it went out, came back, went out, came back and out again, so i didn't think it was a bulb, took it in, the dealership said it was just a bulb. this was last year.

this year, same bulb burnt out again, replaced with a sylvania 1157, bought a 2 pack, i must have used the other one for the same bulb, as I can't find the spare, for the life of me. later this year (about a month ago) rear left shows on the dash as burnt out (hyper flash) it goes back to normnal, i noticed that the turn/brake on the back was working, but the running light wasn't, about 2 days later i noticed that the rear right running light was also out, i assumed because it's a newer bike, all electronic, that it turned the rear right off for asthetic reasons, while the left was burnt out.

a week or so goes by, i didn't have a chance to replace the bulb, the rear left turn signal goes out, i pulled the bulbs, rear left, both filiments were burnt out, rear right, just running light burnt out.

so in the year and a half, between the two rear signals, i've replaced 4-5 bulbs. i spoke with a friend who is a mechanic at harley, he's never heard of this happening, he grabbed another friend who's a mechanic there, heard about it happening on an old, 80's harley, which was loose assembly, causing it to rattle and work harden. we discussed electrical issues, they both guess short to ground would be the only way this would happen, i asked about over charging, they suggested it wouldn't be the case because there would be other issues, i rode last night with a gauge watching voltage, never went above 14.2v, average was 14.0v

any ideas what could cause this? i'm skeptical of short to ground, this wouldn't cause higher amperage or voltage going through the bulbs, this would cause lower, and the bulbs to last longer...

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Have you ever dropped an incandescent trouble light? Notice the bulb never survives. Same situation on your bike. Bulb lit and TONS of vibration = toasted element.

that makes sense, but wouldn't this be an issue on all bikes, or even all bikes of this model? the two mechanics who work on these bikes every day have no idea what could cause this, and it's not like it's a little more often... the two lights that have been burning out, since i bought the bike, i've been having a bulb burn out on average, every 2000km, or like every 1200 miles. This is astronomically high.

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I wonder if the bulb is getting a particular frequency that just due to bad luck is hitting a resonance and breaking the bulbs. I've seen parts of car and bikes vibrate but not all of the same cars or bikes exhibit the same vibrations. For example, maybe on your bike if the light is mounted to a fender, at a particular engine RPM, the fender may noticeably vibrate but then slightly above or below that RPM the vibration stops. Now on an identical bike, it might not be vibrating the fender at the exact RPM as yours due to variables such as a slightly thicker paint, a slightly more compliant or stiffer rubber isolator mount, a slightly different mounting hole position, and so on.
I wonder too if maybe how the bulb is orientated in the socket may be playing a role. Yours may be clocked one way while all of the others are clocked differently ?.
Jim

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1968 Chevy II Nova Garage Find 2012
1973 Nova Custom
1974 Spirit of America Nova
1973 Nova Pro-Street