Rockin Robbins will be a better diagnoser of your 'failure to impact' issue, but have you watched his video on it, found in the
Sub Skipper's Bag of Tricks thread?
As for your mods, is the Improved Stock Environments a later or earlier date than the patches? How about Realistic Scopes? And, of course, OTC. Just be sure you have them installed in the correct order, and that they're all compatible with each other. Also, corrupted saves are unfortunately a companion to all versions of SH. Several factors are at play there, and all aren't known... Another thing to check for on saving - don't get impatient with it like I've been before, and use TC to hurry things along, such as getting below the thermal, and forgetting to turn TC off while you go through the "Save" process, 'cause a lot of time can pass when you do that...
Edit: Just got to looking at RR's video, and I'm wondering if you're hitting the set buttons twice. Watch the dials as RR hits the buttons a 2nd time, and that might well be the difference. Notice at 9:25-40 especially...