Often I have found that the hardware was over-torqued during manufacture. If, for some reason someone prior to you may have tried to loosen some of these bolts, they likely could have been damaged. Hate to say it, but maybe the part was removed for someone and then a replacement installed by another party. The major issue I've found is damage to the plastic panels from long term vibration, removal and reassembly and even accidents. The mounting sprues / studs on the front cowling will easily strip out as they have self-tapping screws. I have drilled them out and JB welded 6-32 threaded inserts into the studs. These are the steel inserts that have a flange on the open end for spot welding. Some of the panels having molded broken plastic tabs have steel washers JB welded to them. This can be quite time consuming as it usually takes 24 hours to cure the JB.
I have done so much work, I bought the $80.00 hot air welder at Harbor Freight and will be using it in the future. Also have the Metric Tap and Die Set.
Your local hardware as well as Tractor Supply or Lowes usually have drawers of nuts, bolts, screws, etc. that are direct replacements. Another back-up I've found are the Nylon washers and spacers that I've used in various locations. Of course, alignment in installing some screws and bolts is not always easy and can cause stripping. Just remember, if you can do your own work, you may be further ahead than to trust some mechanics.
In one case I bought one of those hammer operated screwdrivers where you hold the body, turn it in the loosen / tighten direction and hit it with a hammer to break it loose.