Small Engines (Lawn Mowers, etc.): Troy Bilt Transmatic 77t, safety switches, transmatic

Question
We have had this mower for about 3 years. Bought it brand new at Lowes. The warranty has expired. It has been working wonderful, except Saturday went to mow and it would not go forward. There had been a slight jerking motion when the mower was in a lower gear like 2/3, when mowing the previous weekend, but in a higher gear say 5 or 6 there didn't seem to be a problem. It will run in reverse just fine. I know that there are a ton of safety switches on it. I also noticed the last time I mowed the blade did not completely stop spinning even though the mower was shut off. I would like to know if one of the "safety" switches has went bad, or if it is the transmission that is bad. I have also noticed that the deck is not sitting correctly and it seems loose. I'm wondering if something has broke or fallen off or loose that might be causing it not to go forward because of the safety issues. We have done maintenance ourselves on it every year, ie: oil changes, filters, belts, blades, etc. I've visited a few websites that say this is the worst lawn tractor to have, but we haven't had any problems until now. Would appreciate any help you can offer.
Thank you.

Answer
I would need a complete model number to know what unit you are talking about, although none of the items you referenced should play a role in whether or not the unit moves forward. I would guess you have a transmission problem, but can't diagnose this way, I would check the belts first.