Audio Track Mixer - Mastering Effect 'tube exciter' Disables Audio

Hello everyone,

I have a sequence with 4 audio tracks feeding into the master track. Each track has its own effects, and the master track has the "mastering" effect applied. When the mastering effect is enabled, audio stops playing. I just noticed that it is only while 'tube' exciter is enabled. I can see the levels moving up and down on each individual track, but not on the master track. Very strange. Any ideas? Not a huge deal now that I've found its only the exciter mode, but strange nonetheless?

Premiere Pro 2017

Intel i7 4970k

32GB RAM

Asus Xonar Essence STX

4x3TB Western Digital Black in RAID 10

GeForce GTX 970 4GB