SimpleDataField returning 8 -eight- chars freezes Forerunner!!

Forerunner 735XT with 2-up data field (may also crash other configurations)
See attached project

But to reproduce
1. create simpledatafield
2. return "12345678"
3. add data field to a 2-up screen on a 735XT (may affect more)
4. entire session crashes with no exceptions thrown

result - activity and entire watch freezes with no errors in logs. no CIQ_LOG etc
8 digits seems to be the next stage for fonts sizing so I'm guessing it's something within the rendering?

This is such a simple bug it's stopping me returning something as simple as a time 12:34:56