Convert to multisport skips laps and distances

I have an Ironman tri activiity from back in the days. It's recorded with a Polar watch, and imports OK as Other. It contains all laptimes and distances as one block.

I use the Convert to Multisport functionality, and it is straight forward to split into legs swim/transition/bike/transition/run. But all lap times are gone, and distances are totally wrong, the swim leg is 4 m, bike leg is 200m and the run is -150m.

Pace is messed up too, but the pulse data seems to be correct.

Anyone noticed this before? Did I miss something obvious when converting?

Regards,

/Pär