Rek'Sai bugged tunnels in ARAM?

Has anybody else experienced this?

Was just playing an ARAM, other team had a Rek'Sai. Had a tunnel by our Nexus that was unable to be destroyed, and could just continuously head from his base to ours? I understand his ult, but it was literally a continuous thing. If he'd die, just pop right back up by our Nexus turrets etc..

Even at max rank, and 45% CDR, his ult would still have a 39 second cooldown... (He did not have 45% CDR)

Am I missing something here?