Odd solution, but I can see it being effective. Having to deal with vibrations on a PCB is not a new thing.
Outside of my pinball stuff my full time job is actually in a factory that builds boards used in high vibration environments.
We're talking units that are attached to pump heads, and things like that.
For large thru-hole devices like these one solution is to use an RTV silicone, applied liberally.
A common one is Dow Corning 3145. Electronics grade stuff does tend to be a bit pricier than 'kitchen and bath' types.
The good thing with an RTV is that it can usually be peeled away to allow rework of the PCB if necessary.
Given the layout of the board, and its location, I'm actually surprised there's no kind of anti-vibration materials added.
A good contract manufacturer has a lot of possible things to offer in this kind of situation.
Underfill, potting encapsulation, overmolding, heat-set surface mount adhesives, staking epoxy, lots of stuff.
Not just the TO-220's on there either. The electrolytic capacitors, connector bodies, and that inductor are all potential vibration targets.