Octy II climate occsionally blowing hot

About half a dozen times now the climate control in my Octy II has decided that it wants to ignore the temperature I've set it at and blow hot air at me.

With it set to 18' or higher it blows like it should do when set to maximum heat.

If you turn it down to the minimum setting it will blow an arctic gale as normal.

Stopping the car , turning it off for a minute or so then restarting clears the problem. Turning the economy mode off and on again doesn't do anything at all.

I've not taken it back to the dealers yet , fully expecting them to tell me that there aren't any fault codes and am I sure I wasn't imagining it , but it's now happened several times so it's not going to go away.

I know I've seen a mention of this behaviour from another owner so it's not a one off.

Before I do get them to have a look at it , has anyone else had this remedied in the past? If so what was the problem?