It would be great if another pscan customer with a similar car could replicate your test.
I don't have access to a TF.
It does sound a bit strange.
On the Rovers the Pektrons are a bit vulnerable to water ingress because the wiring loom enters the top of the Pektron so any water that gets through the bulkhead on the wiring loom runs down it and straight into the Pektron.
On my 25 I have turned the Pektron upside down so that the wiring loom enters the bottom of it.
I don't know if that's applicable to the TF or not.