Epileptic stargate?

[Eternal Density]

A common symptom of bad/failed gate connections is that kind of shaking. See: SG-1 season 1. It used to always shake until they got the energy levels sorted out, and then there was Solitudes where trying to dial one Earth gate from the other resulted in shaking. So it's not a surprise that trying to dial a gate with a blocked event horizon would result in some shaking.

[Avenger]

i reckon because the gate was burried it was a bit unstable and as a result started to shake or vibrate when in use. normally the gates "stand" for want of a better world would prevent this and keep the gate stable while in use

That makes the most sense to me.

[Super Carl]

A common symptom of bad/failed gate connections is that kind of shaking. See: SG-1 season 1. It used to always shake until they got the energy levels sorted out, and then there was Solitudes where trying to dial one Earth gate from the other resulted in shaking. So it's not a surprise that trying to dial a gate with a blocked event horizon would result in some shaking.

Also, these gates are older than the ones in the Milky Way. They probably have "glitches."