The issue of reliability of single triggers on doubles needs to be put to bed once and for all. Single triggers whether mechanically reset or reset by inertia are inherently simple. The single trigger double shotgun or rifle still has two separate locks exactly the same as the double trigger iteration of those guns, it is only the trigger that is different.
Westley Richards have for years provided single trigger options for their double guns, Pondoro Taylor himself liked the WR single trigger and stated he would have no hesitation using for his DG game except because all his other doubles had double triggers, he did not want to introduce a possible confusion factor into his gun battery.
The double trigger is just a carry over affliction from the days of unreliability of firing pins and springs in many of the gun locks of the day, the trigger mechanism was not the issue on double guns.

Competition shotgun shooters who fire hundreds of thousands of cartridges during their lifetime rely on perfect repeatability of grip and length of pull of their guns, the trigger of which is a critical part of this. They would not tolerate the slightest hint of unreliability of their single triggers during competitions. The most ardent double rifle owner would only fire a fraction of the cartridges than what an average, let alone a top competition shotgunner would fire in their lifetime.

In relation to single trigger O/U guns, to state that "its just a matter of time before trigger mechanism gets gunked and fails" then I say the owners of such gunked up guns deserve to be trampled, gored or bitten by DG. That is just a poor excuse for stupidity and should not be a reflection on the reliability of any gun. Just as a hunter should be double checking his ammunition and other items and accessories before heading off on an African safari, so he should be doing so on his guns.