I assume you meant that you got a new "step-down transformer" that converts 220 volts AC (alternate current) to 110 volts AC (alternate current) for the use of a "US-Market D8B" in Europe?
Just making sure you're not trying to send DC/Direct-Current voltage (like from batteries - what comes out of wall power outlets around the world is always AC, not DC) into the D8B. That would be wrong and would cause problems and potentially damage.
But I don't think there's 2000 watt AC to DC converters (unless maybe for car battery chargers or similar), so you likely have the right thing.
As long as this is a transformer that converts 220 volts AC down to 110 volts AC, the problems you experience are likely NOT because of the transformer. (It will run on 50 cycles in Europe instead of 60 Hz... but if anything, that could result in a different ground loop "sound" but doesn't usually cause problems for "most" devices).
I think a 2000 watt transformer should also be big enough to deal with the power draw from the D8B. I think the D8B draws less than 700 watts during normal operation... and I'd think that a power-on spike that could be higher, should still not be a problem with a 2000 watt transformer.
I'd think it's just because the D8B was moved from one location to another, and some of the ribbon cables or cards on its inside got loose and don't make contact the way they should. A very common issue after moving or shipping a D8B, if it gets rattled a little, in transit.
I'd go with the "standard" reseat ribbon cables procedure for starters.
Did this D8B work for you, before, in the location where you had it before?
Does it boot up fully, otherwise? What's shown on the built-in display on the D8B when you the V-Pot indicators don't respond? What's shown on the PC Monitor that is connected to the D8B rack unit when that happens?
...oh, and if "took out my OLD D8B" meant that you didn't use this D8B in a long time, also make sure that the battery on the motherboard didn't go out. This would mean that the BIOS lost all it's settings, a new battery would need to be installed, and then the BIOS settings would need to be set to what's described in the database, here:
https://www.sonido-7.com/d8b/maintenance.html(First article on the page - you'd have to figure out if you have the "old style" D8B motherboard or the "new style" one - the BIOS settings that need to be bade are different for them).