</font><font color="blue" class="small">( Hey Jinman ....... your thoughts.... )</font>
Sorry I missed this earlier, but way back when I first got my TC45D, the parking brake lever would seem to get stiff in it's operation for no apparent reason. It was so bad that it was hard to pull up to engage and when I stepped on the brake pedal to release it, I had to push down on the handle to get it to release.
I found the two pivot points for the handle were overly tight. I took them apart and cleaned the bushing and lubed them a little and since that time I've not had another problem. It's my guess that that is what's happening to Matt and the other gent who posted this problem initially. The only reason I can think that would make it a problem when the tractor warms up is the natural warmup of the running gear might transmit heat down the parking brake mechanism and make an existing problem a little worse due to metal expansion within the bushing. Not sure. . . but that's all I can come up with.