1998 Isuzu Trooper Hard shift up and down

1998 Isuzu Trooper. 71k miles. 6cylinder. 4wd. Auto trans. We recently moved from California to Maryland and drove the Trooper the 3000 miles loaded with two adults, 2 dogs, 2 cats and bare essencials. We had a trusted family mechanic do a full workover on the Trooper before we headed out and I asked him to take special interest in the auto transmission. He did so and said everything was ok and since the fluid was still clearish-red that he wouldn't recommend a fluid change until after we got to Maryland. Trooper drove superbly during the trip and for two weeks afterwards.

Just the other morning, (temp in the low 80's like it's been for a while) we got in and it shifted real hard from 1st to 2nd, 2nd to 3rd and when we slowed down shifted hard from 3rd to 2nd but normally from 2nd to 1st. The hard shift is like a "jerk" as the engine revs a bit higher than normal (not extremely, but noticeably) and then the transmission shifts. As for downshifting, it seems to wait a bit longer before downshifting than it used to before a "jerk" as it downshifts. Doesn't miss any gears as it shifts though and no weird sounds or movements in steering. No loss of power and the accelerator is just as responsive.

I checked the transmission fluid (no dipstick so I read online on how to check it from below) and the fluid is SLIGHTLY darkish red but still very redish. No smokey smell, no streaks and no metal flakes in the little bit that dripped out on a clean paper towel I held underneath. BTW: I know what smokey transmission fluid smells like as our Ford Explorer trashed it's auto transmission a year ago.

Another strange thing is the gear selector indicator in the dash isn't always correct. For example, sometimes when I move from Park to Drive, it flickers between P and D before settling on D. Sometimes, there is no indicator light denoting a gear when I shift from P to D. Also, when I shift from P to D, the transmission shifts harder than it used to.

Any idea what could be going on? This doesn't seem 100% like a transmission problem, but then again I'm not a mechanic. I've made a $10 donation in the hopes you guys can help us out.