For the first thing, it's a Philips. I have an absolute hatred for anything
Philips, bad quality and poor soldering /design.

Rant over, the most likely culprit is the line output transistor has gone
short circuit or leaky. So, take off the back and resolder all of the pins
on the line transformer. Grab a multimeter and do a diode check on the line
output transistor. If all 3 pins read almost dead short then it's fried,
probably 95% of the time you can just change it and the set will be fixed,
although in that nice rare occasion, it will work for a matter of hours or
days and then die again, pray it doesn't.

If the line TRX is not short circuit, then the transformer may have died or
a rectifier diode from it may also be short circuited. The twerp sound you
are referring to is called hicupping, more common in older Philips TV, ie
KL9A, KL9A2, which would often be either S/C line TRX or faulty high voltage
pack or tripler.

Paul