Is there a chance to enhance the transmitter Power of the VM108?

Sorry, no such modifications.

what could be the problem, that my receiver, I guess it’s a VM109, doesn’t work as good as in the beginning anymore?
What I’m trying to say is, that the range of all my Transmitters is very limited.
I can hardly turn it on, or off, from outside my house. And that’s only 5m away. It works great inside so.
I didn’d have that problem 2 years ago.
I changed already the batteries of the transmitters and tried to “play” with the receiver antenna.

Would it make sence for me to try extanding the antenna in the VM108?
I saw a circuit path from the transistor to the LED, could I try cutting it to extend with a wire?

Your help would be very appreciated.