[bug] Firefox, indicated length not commensurate to length

[phrokton]

dev branch, current version

Sometimes snake is fortunate to be deemed longer: 12. It appears to be fixed to a two digit length. Snake grows; indicated length does not grow commensurately.

Not so in Chromium (64bit, stable or dev) for the same server in similar load: functions as expected. Only one interweb browser running at any given time, with one tab, application in focus.

GreaseMonkey 3.8
Firefox 47.0.1
Waterfox 47.0.1 (64bit)
windows 10
16 gigs ram
i5