Did you check pending codes? (Do you have a reader to do that, etc.?). This sounds like it could be a failing OCV. It has been a while since I addressed this personally, but I *think* I had symptoms before the OCV/VVT actually popped up. It takes a certain number of duty cycles to generate a CEL. In the interim, detected faults will be stored internally as pending codes and can be accessed via the OBDII interface.

You can take a bad OCV out of the car and bench test it with voltage and the solenoid will act normally. Thus, I have to imagine there is some gradient where heat and pressure can induce malfunction intermittently.

I would start finding an OE pair of them so you know where to go when you get a handle on the problem and if it turns out to be them. Replace them both IMO. I was able to find some Toyota close out parts and got both genuine parts for about $90 total from Ebay, so shopping around for “real” ones is better than grabbing aftermarket ones. Some people have reported the aftermarket ones simply refuse to work.

I don’t think you really know any more today than you did yesterday - replacing the OCVs with Dorman units and seeing no difference doesn’t demonstrate anything conclusive. Others have put in the Dorman units, had no relief, then tried factory units and had all issues go away. There are a few reports of that both here if you search, and at TN in corresponding Camries.

In the absence of a VVT code, I would check the other commonalities to those cylnder, one being fuel supply to the bank. I don’t know how the cam position sensor on these mounts as I’ve never had to service it on this car, but that’s another place to look.