It seems like a perfectly good idea when cleaning a cooker hob, to remove the burner caps and put them into hot soapy water while cleaning the top of the hob.
However, it’s better to leave the caps on until the rest of the cleaning has been done, and only then clean them, if necessary.
The reason for this can be seen looking down on an uncapped burner. Down below in the centre is a piece of metal with a central hole. This is the injector, and the gas to be burned passes through it.
As is evident, the hole is quite small. With the burner cap off, it’s quite easy for liquid to fall into the injector, leaving a residue. In time, the residue will build up, gradually blocking the injector so the burner
produces less heat and ultimately may cease to work
Cleaning the injector is not necessarily difficult for a service engineer, so don’t throw your cooker away if it blocks, but it’s better not to have the problem in the first place. On no account poke bits of wire into the injector in an attempt to unblock it as it’s quite easy to cause damage.