Strange TH3 Latency Issue

Greetings,
I'm working on a project with 15 tracks, a moderate number of efx (mostly EQ and console emulators).  Everything worked fine until I tried to record a new guitar track using TH3.  There is obvious latency when trying to record along to the existing tracks.  I have done all the usual stuff to reduce latency to no avail.  So I tried turning off all efx in the project using the FX button in the Control Bar and it didn't help.  I then re-enabled all efx and started turning off one effect at a time starting at track one.  Track one has an LP64 EQ and a Midnight Compressor 64 in the efx bin.  Nothing changed when I turned off the LP64 or the Midnight compressor individually. But when I turned off both efx by turning off the efx bin, TH3 started working fine.  No more latency from the TH3.  But WHY? 
 
   So what does turning off the track 1 efx bin do that lets TH3 work as expected and how do I make this situation go away?  And, yes, I can record the new guitar track with the track 1 efx bin turned off but it seems like I shouldn't have to do this.  Anybody have any ideas?
 
Thanks,
Bill

Thanks a million, scook.  You gave me a very concise answer that explained exactly what was happening.  I will try setting the VST3 LP EQ precision to non linear and see if that does the trick.  Otherwise I'll either replace the LP EQ with another EQ that doesn't require the look ahead buffer or I'll just record the new guitar part with the efx bin turned off.  Your answer made me feel a lot better since I now know WHY the latency was showing up.  I was worried that something had become corrupted in my project (a project that has taken *years* to bring to fruition) and I couldn't have survived that... ;>)
 
Bill