Those tail lights could be the brake lights you are seeing and that would be a faulty brake light switch or the brake light switch is out of adjustment.
Brake Lights Don't Turn OffUsually this issue is caused by an improperly adjusted brake light switch. Sometimes it could be a defective switch, but this is rare.
Check bulbs Fuse Stop light switch
Brake light switch failure, bad ground wire at rear of vehicle or fuze blown.
Check the switch on the brake pedal
the plug behind the battery might be unplugged or that same plug is disconnected from the fuse box
replace the break light bulbs?
that sounds like i ground in the bake by the lights or if it has a trailer plug i would start their
brake switch ???
Alternator has/is going bad.
Try the tractor with a different trailer, the pig tail is most likely not connecting properly.