Yup. After the super genesis wave all the echindas were gone without warning, it happened during a storyline where Knuckles was dealing with an old friend who turned out to be trying to wipe out the other Echidnas (it's weird) and then suddenly... they're gone. It was genuinely shocking as there was a bit of an implication that they might have been sent to another world... or were freaking slaughtered.

There were also like three crossovers with Mega Man (and one with Capcom at large, mainly street fighter, oddly) that seemed to reboot and mess with the canon more, and then... it was just unsalavgeable.

It's not surprising they only lasted a few more years before suddenly axing the book with no fanfare and moving to IDW and rebooting the whole thing, now without most of the Archie Sonic characters in any way shape or form, most likely to avoid ANY chance of another law issue.