Sending data from 4 transmitters to 1 receiver without a microcontroller
If, as I read it correctly, you have 4 independent FM transmit modules and no means of time-synchronizing them, this won't work. The 434MHz FM receiver is usually designed to receive any FM transmission over a bandwidth of about 1MHz. The receiver will lock into (after a delay of a few milliseconds) any single FM transmission and, if two transmissions are present it will get into a mess.

However, if you can route the switch wiring to one transmitter's HT12 module then this should work effectively. If this is what you are actually doing (unclear in your question) then the problem lies elsewhere.