On Mon, 08 Jul 2019 15:52:32 +0200, I wrote:

Could the blown capacitor be the only problem, or is it only a result
of the actual fault?

The capacitors arrived. Out of curiosity, I reinstalled the old
transistor and tested the charger (without the capacitor). The charger
started up normally, no fuse blowing. Then I added the new capacitor
and ran the charger at full load for about 15 minutes with no
problems.

In the meantime, I also bought a cheap megger and tested the blown
capacitor at up to 1 kV. It does show some conductance, but it is in
the hundreds of kohm range, so it should not be able to blow the 5 A
fuse.

So, the charger works again. Although the blown capacitor seems to
have been the root cause of the problem, the analysis does not quite
add up. Maybe there is an intermittent problem somewhere?

Thank you everyone for your comments.