Stuck on channel
This looks to be a problem either on the IR circuit board or in the microprocessor that controls these features and controls. I would suggest since you have tried to change channels from the TV itself that the problem in the processor is the more likely option. In this case I would say since this would involve a lengthy troubleshooting procedure, That you may have to take your TVs to a qualified TV repair facility for servicing since the procedure may be beyond just replacing a part, and may involve actual electronics troubleshooting. Having owned a shop for some time I can tell you that some items are only repairable at TV shops.
I hope this helps,