R15b5 : FUSION : Track Hanging

Are there any tips on how to increase the chance of a FUSION Tab CameraTrack being able to Solve the Auto Track without Hanging?
+) I've tried using lower resolution footage (eg 1080p footage from an Ipad)
+) I've tried using short clips (eg 100 frames)
+) I've tried limiting to Track points to those with a minimum track length of 15 & 300ish track points
Symptoms:
+) When Solve is clicked -> popup shows progress to 99% -> the Popup Closes
+) Resolve then hangs (ie no 'Solve Error' is calculated - and processing continues indefinitely - mostly on one core)
MISC : I note that FUSION is able to process shorter clips (say 15-30 frames).
It just struggles when the clip is more than couple of seconds.
Has anyone else had any success with FUSION Tracking inside Resolve?
AJ
+) I've tried using lower resolution footage (eg 1080p footage from an Ipad)
+) I've tried using short clips (eg 100 frames)
+) I've tried limiting to Track points to those with a minimum track length of 15 & 300ish track points
Symptoms:
+) When Solve is clicked -> popup shows progress to 99% -> the Popup Closes
+) Resolve then hangs (ie no 'Solve Error' is calculated - and processing continues indefinitely - mostly on one core)
MISC : I note that FUSION is able to process shorter clips (say 15-30 frames).
It just struggles when the clip is more than couple of seconds.
Has anyone else had any success with FUSION Tracking inside Resolve?
AJ