MirW multi point to point

Hi, not too sure that I am posting in the correct place but here goes.
In December 2017 I purchased a MirW reciever (sku MIRWR45_2MILE) and 3 single transmitters.
All four units have the following antennas https://www.gowifi.co.nz/omniaaa/ant-53.html
The transmitters are each in a centre pivot irrigator and signal a pump to run when any pivot runs requiring water. They all worked well for around a year but recently have been latching on the reciever when pivot shuts down. Initially one unit was causing the problem, then a second one joined in, now I think all three are. The signal at the trans is defintely ‘off’ but the reciever still shows it is getting a signal to close the corresponding relay. After cycling power to the reciever it opens the relay (when the trans is off).
I believe the power supplies at the pivots are ok, power to the reciever is from a NCD 12v regulated switcher supply. Signal strength was tested at instalation using XCTU and was good, each transmitter could ‘see’ the reciever. I set up the xbee’s on a random channel to try to avoid any interference.
Any help/suggestions would be appreciated.

Are the loads at the receiver wired to the NC or NO connection of the relay?

What is the load being switched at the relay end? Is it a power load or are you switching a contact?

Is the power supply at the transmitter shared with any other devices?

Another thing to check is the antenna mounting, if the ground of the antenna is touching anything conductive it can effect the transmission and power regulation on the wireless module.

Hi Jacob
The load (input to a smart relay) is wired in parallel across the 3 relays N/O. The LED is staying on on the PCB of the receiver indicating the transmitter is sending a signal when its not.
Power supplies at transmitters are not shared with anything else, I mounted them in die-cast Aluminium boxes to try to avoid any interference, as its all mounted in large steel cabinets for a pivot irrigator containing D.O.L motor starter for approx 11 H.P 3 phase motor.
Will check the ground of the antenna next time I’m onsite.
Thanks for your response.

You’ll know if one of the wireless modules burned out if its hot on the bottom of the board.

You might also want to try disconnecting the contact at the transmitters when this is happening and see if the corresponding relay goes to the NC position. Test it a couple times with just a jumper wire. If it reacts normally then you may want to look at the contact closure coming into the transmitter inputs.

Also is there any voltage on the transmitter inputs or is it a dry contact?