Maybe it was this server’s plan to do that?

I did a quick calculation and:
2220 * 0.7 = 1,554.
That’s the exact same as:
(444 * 5)*0.7= 1,554.

The 0.7 there is tax, which occurs when a player sends robux (mainly via purchases)

To my knowledge, group payouts DO NOT have this tax. (As this forum question by another user shows) And this tax is usually on Purchases, so they must’ve sent you them as payments rather than payouts

This group could’ve easily sent you the full 2220 robux without any hassle via group payouts provided you joined their group.
Why did they send you robux in 5 separate amounts then?
My personal suspicion is that they might have made it look like you hacked into their account and stole their robux, which would obviously raise suspicions on Roblox’s if they happened to report this.

The best way to resolve this, probably, is go into more detail in another appeal about how you withdrew this robux. (Provided there’s not another one ongoing)
Any proof in the server? maybe the Group itself?
Maybe you could tell them how you received separate robux payments rather than one group transfer.
With those, Roblox would probably get more detail on your case and HOPEFULLY realise you are indeed, a normal player.

Again, hopefully your account gets un-terminated soon, and Good luck!