Short circuit: the basics

[Topwater Elvis]

Remove #4 from #5, #4 has the male end of the 510 connection, #5 houses the female end of the 510 connection.
Any contamination in these areas will cause problems like you describe.

Below, This is the 510 connection point, the brass looking round pin in the battery/power device can get depressed and cause issues like you're having.
The silver looking pin in the delivery device/tank can also get stuck inward from gunk/residue build up causing connectivity problems also.
Both sides of the 510 connection including the threads (battery/power device to tank/ delivery device) have to be clean, shiny, free from any liquid, goo, gunk, build up and or debris.

You also have to make sure you’re using the correct CL heads, only the 1Ω and .5Ω will function correctly with your power device. ( black O rings on heads )
The CL-Ti and CL-Ni (red and blue O rings) should not be used with your power device.
Make sure you’re using authentic joytech replacement heads, the knockoff, clone, copycat, fake heads are notorious problem causers.

 

[BrotherBob]

Well, and today it's working for a few hours w/ out short circuit. But since I am planning to go to the store anyway, I will take it with me and tell them my experience...

Welcome and glad you joined. Good luck on your quest to fix. Store should be the most help.
Might like to read:
Learn About Vaping Here - Everything Ecigs - From Beginner To Advanced
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(1) Proper Terminology - Is it a carto, a tank, or what? A Guide to Juice Attachments. | E-Cigarette Forum

 

[Tadej]

Thank you BrotherBob and especially thanks Topwater Elvis for your informative replies!

Now the vaporizer is doing that much much less often (like once per 1-2 weeks). Also, I need to correct the info from original post. When the vaporizer gets short circuit, the ligh actually flashes 30 times, not just 5-10 as I wrote.

Finally, I got my hands on another type of head that I also bought in the same store as my other device – it's the .5Ω head (CL head I assume?) and with it you don't need to replace a head every 2-3 weeks with a new one (one is 3-4€), but instead you just replace the coil & wadding yourself. (I don't know why the guy in the store haven't told me about it the first time I bought a replacement/new head)

Thanks again for all the help.