Hello

maybe you have to check correct tracking weight, I've had many turntables, any B&O, on which I've always play 12" 45rpm vynil without problems.

Have a nice Tuesday

MArco

+1 on checking the tracking weight, or maybe the whole vertical tracking mechanism, if it looks like the weight is set properly.  

A less-likely reason for groove jumping can be warped vinyl (or rarely, off-center hole vs. grooves).  45 RPM vs. 33RPM exacerbates the problem, as the dip (or eccentricity) whips past the cartridge faster thus the negative acceleration at the tip of the arm is greater.  However, 12" 45's of heavy weight vinyl as you describe, typically being audiophile pressings, are less likely to exhibit such problems than 7" 45's of 1970s pop music or old, abused, disco/DJ pressings.  (Of course any such problems are worse on the short-arm B&O turntables, where the distances are closer and an irregularity is more likely to bottom out the stylus and bang into the cartridge.  There was a reason turntables that had to play 78 RPM and early 33 RPM records had tonearms that looked like this:

I set the balance several times according to the Sound Smith instructions.

https://www.sound-smith.com/how-balance-your-bo-tone-arm-and-set-proper-tracking-force

Maybe something wrong here ?? 

Vinyls are completely new, straight from the foil

New facts,

I checked everytgink one more time and... Both 45rpm vinyls weigh about 200g (on albums it is written that they are audiophile 180g).

So I bought another audiophile album 180 g but 33 rpm. And ... the same problem. The needle jumps and falsifies sounds.

So I went the other way and I used the regular disc (not 180 g) for 45 turns and it's just play faster but clean.

I checked if there is a problem with measuring the weight inside of Beogram. Before the start, I put 20 g of weights on a regular vinyt ( vinyl + weight had weight a real 180 g vinyl) and the problem did not occur at 33 rpm and 45 rpm.

Problem in MMC after retip?

Is the anti skating adjusted correctly

I'm no expert, but notice that the jumping happens to correspond with the higher volume break of the song?  Also you're playing at the outer edge of the record?  Such behavior could be an anti-skating control messed up... BUT there were plenty of threads years back about how these turntables didn't have any problem with their anti-skate controls but rather had dried-out lubricants.  Get down at eye-level with your platter and see if the stylus cantilever is tilted while playing, possibly hard to the right (\).  It should be basically vertical, sometimes very slightly to the left of center because the record is dragging the stylus in and the cartridge and tonearm follow.  (Or very slightly to the right because the anti-skating control is trying to counteract that.  But the keyword is "slightly".) It looks like you're skipping ahead and not behind, so you might try it on a loud track near the middle of the record instead of the outer edge?  Yet I don't see any reason for this to be worse at 45RPM, which is where you started.  Maybe the extra-heavy vinyl is thicker and raises the end of the tonearm enough to change the geometry of the stylus on the record -- it would *already* have to be broken or mis-adjusted in some way, but was borderline and thick record exacerbates it?  Sorry, these are all wild guesses, and I don't have any experience with how re-tipping can go right or wrong, to help you with your initial suspicion.  Of course the easiest test is to bring out your "spare" turntable and your "older" cartridge, and swap them around.  Difficult if this is your only setup, I know.  Particularly difficult if you have never seen this particular turntable working with a cartridge before your re-tipped MMC4 and don't know what to expect.  But at least these are things to try until a true expert offers you better advice.

check distance as in pic for "normal" and 180 gr. LP

I did some experiments :

- When I put on a thick vinyl, regular vinyl (I have two vinyls on a turntable together), the thickness is much bigger but the turntable plays normally.

- When I put on turntables plate distance ( about 0,5 mm or 1 mm ) and on top I put regular vinyl, turntable plays without problems. 

Looks like problem is realy in 200 g vinyl