R34 GTT - Interesting 4th gear grind only when...

[Doug 98 R34 GTT]

Hoping someone can shed some light on this...

All 1 - 5 shifting is smooth, all 2 - 4 down shifting is smooth EXCEPT when I'm in 5th, go to neutral, then down shift to 4th (speed matches 3rd/4th, could've possibly been a bit slow for 4th). It grinds and won't go in, almost feels like as if the clutch is not pressed in. I typically don't go to neutral then 4th, but today I did for whatever reason and noticed it. It will happen every time, but if I go straight from 5th to 4th, zero grind, very smooth. Super odd. I haven't tried double-clutching to see if that helps, but tbh, I'll just never go to neutral, just wondering what would cause it to grind only in that scenario. 

[GTSBoy]

Speed mismatch coupled with some synchro wear.

Gearbags are not full of magic. They have their limits.