Should it be difficult to move the gantry up when powered off?
It is very difficult for me
My Zero is hard to move when off.
Motors, belt tension, gears & pulleys all have to move in 4 corners where as a bed slinger just has to move up.
“Difficult” is a subjective term.
If you manage to raise it perfectly level it will not require a large amount of force. If it tips it wedges and becomes hard to move.
In general I’d advise manually raising a flying gantry like the SV08. If you must then raise one corner at a time a short distance. Don’t force it you could bend the gantry and/or damage a linear rail.