4wd light comes on at random when in 2wd (and other 4wd anomalies)

Fairly new to the Tacoma...bought my 2010 back in April with about 160k on it, and we love it. Just added an ARE canopy. It already had about a 3" lift kit on it--looks like just blocks under the springs, etc, no custom shocks or anything that I can see, but still learning. Automatic tx.

Right off the bat, we ran it through its paces in all kinds of WA state spring weather: snow, mud, water, gravel, pavement. No serious off-road stuff or any spinning trying to get un-stuck, but lots of dry and wet dirt roads, so a lot of in and out of 4wd. Mostly 4H, a very small amount of 4L.

From the outset, I could see first the 4wd indicator on the panel blinking as soon as I switch into 4wd (L or H), then a click behind the driver-side console, then, at the moment we could feel 4wd actually kick in, another click from somewhere behind the glove box, and the 4wd goes solid. That seems all correct, and it was rock-solid and consistent for a couple of months.

After a couple of months, though, we found that the 4wd would not kick in consistently, whether in neutral, sitting still, driving (we never shifted into 4wd at anything over perhaps 15 mph). Now things have devolved this:

1. When in 2wd, the 4wd light will begin flashing. Not every time we drive it, perhaps every fourth or fifth time. I am not sure if it always starts while driving, always when starting the engine, or some of both; I just notice it on while I am driving sometimes. It never actually shifts into 4wd in this mode (which is probably a good thing, since the switch is still in the 2WD position), but the light just continues to flash, ad infinitum, until I turn the engine off, pull & reinsert the key, and restart. Even then, it can take 2 or 3 iteration of all of that before the light will stay off. It will not shift into 4wd, and I hear neither of the relay(?) clicks when I turn the switch into 4wd while the light is already on.
2. When I do want 4wd and the light is not flashing it will not go into 4wd consistently. I often (or maybe always by now) have to shut down the engine, remove the key, re-insert the key, and then retry 4wd. When I do get it into 4wd, it will sometimes get stuck in 4wd, ignoring the switch back to 2wd. In all of this, I never hear the dash/glovebox clicks unless it actually shifts, and it never shifts unless I hear those.

Now, I have not empirically tested every combination of trying to get in or out of 4wd with engine on/off, switching while in forward/neutral/reverse, and going forward/reverse after shifting to get it activate, so it is entirely possible there is something consistent here I have not yet identified. I know only that it used to work perfectly but now has two anomalies:

1. I should not see the 4wd light come on when the switch is in the 2wd position, and
2. It should shift in and out of 4wd consistently when I switch in and out of 4wd/2wd.

I have seen a variety of posts on the issue with various solutions suggested. Unlike some, I have heard no odd sounds when shifting in/out of 4wd or when the light is on/off incorrectly. It just seems that the 4wd indicator comes on at random and that the 4wd actuator fails to engage/disengage less often than it succeeds. On top of all of this, I did have the vehicle into a transmission shop to change the tranny fluid. They had to drain and fill five or six times (yes, using the Toyota-specific fluid) before it came clean, so I suspect the prior owner did not keep up with tranny maintenance, but that is another story. While they had it, though, I had them check the vacuum, which I see can be a problem, and they found nothing amiss. Their guess was that it needs an actuator unit replacement but said that "the 4x4 actuator not only comes as a complete assembly, but also requires removal of the transfer case and then a disassembly of the unit"--a $1500+ job. These are friends of mine, so I know they are not trying to do an unnecessary job, but they are transmission guys, not 4wd experts, and I am hoping the actual problem & solution are not quite so deep.

Ideas? Just kind of hoping it is a relay issue maybe and not the actuator motor itself--not as though my best hoping will change any of the facts, of course.