Cub Cadet Yanmar SC2400 transmission odd behaviour

[High Tach]

My granddad recently passed and he left behind a 2011 Yanmar SC2400 with about 530 hours and since he got it in 2012 it has been very reliable. It still is, but the transmission has been acting funny. I first noticed that when I release the forward pedal, it jerks to a stop as if it's pulling something very heavy. The performance doesn't feel that way though. It never felt like the transmission was lugging, even at low RPMs. It used to smoothly glide to a stop, and still does when releasing the reverse pedal. Then, earlier this week, after box blading some heavy stuff for a while, it shifted itself into high range while under heavy load (I later read this was an issue with some SC2400s, could not duplicate). This freaked me out so I stopped and dismounted the box and FEL. I noticed that sometimes when pressing the forward pedal from a stop, there would be some dead range in the pedal before it would roughly engage. It wasn't every time but mostly after backing up. I suspect it has to do either with the control linkage or it's an internal problem with the transmission. I might be paranoid, but I don't want to keep running it with a problem that keeps getting more expensive. He put in a Yanmar hydraulic fluid (the bottle is still there, I can find the type tomorrow) but all of my research tells me it calls for Cub Cadet hydraulic transmission fluid only. I assume it's been the same stuff this whole time, but it's hard to find any specs on hydraulic fluid, especially for this application.

These Cub Cadet Yanmar tractors are quite illusive. It's hard to find information and as I understand, Cub Cadet (MTD) and Yanmar parted ways right around when we got it, so we just called it the Yanmar. We have a JD 1050 for bush hogging and plowing but this little tractor has become essential for mowing and loader work around the house where we have several acres of bushes, trees, barns, and pasture. I'd like to know if anyone has information about anything I mentioned or this tractor in general, I'd greatly appreciate it.