Unstable PVR - suspect Caps

I have a panasonic DMR-PWT530 that has become progressively unstable on the HDMI output, i.e. temporary loss of picture.

So today it drove me nuts and I replaced it with a spare recorder so the TV picture (same cables used) is now always on which confirmed to me it was not the TV but the PWT530.

Recordings do not suffer so it seems to be related to the output.

The right hand cap in the photo has a slightly domed feel and I suspect it may be the culprit and as they are so cheap I have decide to replace all three just to see if it is one of them. they are marked

4hz
220
6.3V

So I can see many 220uf 6.3V caps of same physical size but nowhere any check on that 4hz. So what do I need to replace them.

After a bit of digging - Would the 4hz be simply the Nichicon HZ Series?

That gave me an idea. Knowing that capacitors are quite prone to failing - they are usually the first thing to be considered - I wonder whether there is a case for 'plug-in' mountings on the board for ease and speed of replacement, rather than having to de-solder and solder the replacements.

Or perhaps I'm over-reacting!