Potterton boiler FSB 30HE issue

[Hkphooey]

Hi guys
Sadly seems British gas have given up on my home care call outs.
They haven't turned up the last three times.
My boiler locks out single red light, now heres the thing not always.
And seem to be when I try to use both HW/CH at same time, also when I use CH on its own seems to take a long time to fire up, just lumps slight bang for a few minutes the eventually kicks in.
The fault lights don't come on just a solid red.
Last night heating was on most of the night then went cold and the red light was on. Tried the reset but wouldn't come on, after about a hour it kicked back in and started to work the heating again as I'd it had cooled down.
Any advice on what maybe the cause.
I know I need a engineer but i would rather get a idea.

 

[Hkphooey]

Weird again this morning as I type... Its working as it should do.
But it will lock out later today 100%. Would random lock outs be down to pcb?
I have had BG clean condensate trap out on last visit as was blocked.
Their solution to the problem when I spoke to the engineer on the phone while at work was.
"get a new boiler, this is a nightmare to work on"
When I said I haven't got £3k at mo spare his answer was "we do finance, would cost you the same as your home care payments"
Well he might be a gas engineer but he certainly isn't a math's teacher.

So as it's a bit difficult for him he wants me to spend £3k on a new boiler so it's easy for him to sort when he gets a call out.
Was same engineer last two visits he clearly didn't fancy finding the real fault.
Previous guy before him serviced the boiler, never mentioned anything about a new one.
Also never checked trap on service (which should be part of a service)
When I questioned it to Mr new boiler he said
"well its hard to get to so didn't bother"
Sorry BG your engineer's are rude and not much good, all they seem to want to do is prove and run.

 

[Hkphooey]

View attachment 289789

 

[Hkphooey]

Also after refitting my trap he left the bung loose and it was dripping water into bottom of boiler case and on floor I had to tighten it myself.
This is what I came home to on his first visit, wet blue and just left there, water in puddle on floor too.

 

[Hkphooey]

This was picture he sent.... Perhaps if was checked on service I wouldn't had to call him out twice.