I have never had any problems with the Beyerdynamic cables.
Also have the HP50... but one driver did not survive a test and broke. Fortunately these drivers are found cheap on Ali express (are original ones) so that was an easy fix.
Getting a good seal is important and was difficult at first but later got the hang of it.
2 weeks later the internal wire in the headband broke (my HP50 was second hand) and now can only use it with a dual entry cable.
HP50 is warm, full bodied and slightly 'laid back' in the upper mids and low (but just enough) on treble which has a 'soft' (as in not sharp) character.
Somewhat lacking in 'air' and 'sparkle'.
HP50 has a pleasant warm 'tilt' to it.
A bit speakers in a room that has a lot of curtains and carpets in it.
DT990 is warm and bassy but does not have the bass extension of the HP50 (with a good seal)
The mids feel a bit 'recessed'. The treble is sparkly and sounds very detailed but is mostly because it is elevated .. a lot.
Some like it, some hate it and call it 'sharp' or 'piercing'.
So warmish, a bit like HP50 but less well extended in the lows. Treble is 'detailed', sparkly, and 'bright' but not coarse/harsh though.
Opposite of HP50.
Comfort wise the DT990 does not feel as claustrophobic as the HP50. Build quality wise the DT990 is better and can take a beating both mechanically and electrically.
Needs amping unless 32 Ohm version.
HP50 is best driven from low power devices.
Don't know the HE400 (but do know the HE400i) so can't comment other than the SMC connectors and HIFIman reputation.
Both HP50 and DT990 are very 'forgiving' headphones and can sound good on most recordings (when you can get past the treble peak for DT990)