Well i know theres a lot of things run on the 433mhz band Ie the rfid (nfc) , some wireless kit . Weather stations, could go on all day. As this is the older mk1 i suspect its interference from a mobile phone nfc or wireless scanning.
Also on the 433mhz range (band) theres a limited amount of time you can broadcast a signal .
So in a nut shell without knowing what kit the op is carrying phones tablets car keyfob ect.
Where the gentleman is fishing . Ie near houses business park ect.
Cant solve the problem.
Sent from my SM-G928F using Tapatalk