I just logged this issue in the Bug Tracker (id# 14030):
When exporting a survey in the tab-separated text format, any group-level relevance equations are lost (i.e. they are missing from the exported file). Question-level equations are apparently unaffected.
Confirmed on v3.14.8 build 180829.
This issue really tripped me up earlier today with my test-takers. Hope it can get fixed soon...