Voltas — voltas split ac 1 ton (inverter)

Raised a ticket on 14th may for f0 error which suddenly started coming in one of my 2 ac's (Same model number)
Technician came, took rs 400 and went back saying that we need to provide him a photo to ensure there are no issues, we provided the photo and then technician said that its due to heating that the ac gives f0 error, however, we have never seen this error on the other ac in other room
We have been struggling with voltas customer care everyday, they open the same ticket, assign the same engineer and he refuses to do anything
Please help and advise