I've had this too.  Could the join where the black bits meet filler have not taken the clearcoat properly.  If this is open the solvent from the gel can get under it and cause  paint reaction.  Best way I found around this is to use a two pack primer first and then clearcoat it.  As has been mentioned the clear needs to be fully cured which can be a good few weeks at room temp.

So, update of today!

All gel coat was taken off, easy with air, so, I am happy with my waxing work!

Clear coat has wrinkled up! So, no more that clear coat!

Also this plastic reacts very strange with acetone!

In end off day I have taken off all clear coat, so now I am again in starting point!

So, give me some suggestions how and with what to cover my hood and especially that plastic part!?!?!!???  Maybe I should stay only on primer, heavy primer coat!

There are two common causes of this problem... which is called "ALLIGATORING".  I used to get it a bit when I started out fibreglassing thirty years ago.  The first cause is a chemical reaction when you apply resin over Gelcoat where you have not applied the Gelcoat thickly enough.  The resin going off over heats the Gelcoat.  This is not the case here as you haven't applied resin yet.  The second & obvious cause is a chemical reaction between Gelcoat and the sealer used... and this is obviously your cause.  It could be because the sealer hasn't cured fully.  I know you waited a week, but I gather you're in the UK and a week there is not quite as warm as a week here in Oz!  Sunshine or heater lamps might have been needed... who knows.  You can only try different things and learn as you go.  Just don't get too discouraged.  Press on despite this stuff up.

If I were in your shoes I would be trying another gloss sealer.  Wattyl Estapol 7008 two pack floor varnish is what I use.  A US equivalent is Camowood Glaze coat.  Do the whole exercise again on a small piece of scrap to make sure you've overcome this reaction, and to restore your self confidence.  No point wasting more time & materials in doing your learning here.  Another alternative is to use your fiberglass resin itself as a sealer. 

You're gonna have to peel all this wrinkled Gelcoat off your die.  Start with a small bit in a corner & see if the alligatoring is occurring in the finished surface too.  If it's not - then just glass over the Gelcoat... but I expect it will be going all the way through your coating.  The other thing you could try is to sand you die once it's cleaned off.  Check to see if it powders.  Any stickiness would indicate it's not fully cured.  Then maybe try a second coat of the same sealing epoxy resin to double seal your mould... once again on a small sample. 

You are smart enough to learn whatever the trick may be here.  Gaining that knowledge through persistence is what will set you apart from the try hards.

Just seen your update here.  It looks from those last pics that - apart from needing to try another epoxy die sealer, you need to do a little more work with car bog to get your die smoother.  That is unless that ribbed effect in your bonnet is what you're after.  Your problem definitely lies in die preparation & sealing. 

The times I have had an issue with the gel coat wrinkling its been because the temperature was low and the gel took a long time to go off.

Hi all again!

I would like to know ---- will 2k epoxy primer hold gelcoat out from wrinkling! 2k Clear coat is very expensive think here in Denmark!