in the GUI, that dark synchronise screen, if “Progress increase per hour” goes negative, then “Estimated time left until synced” says “%n left”, not integers, but ‘%n’. I was expecting a meaningful wording, like “unknown” or “infinity”.
can you reproduce the problem?
I get this behavour by suspending a non-synced node for a few hours and then restoring it.
What version of bitcoin-core are you using?
0.15.99
machine:
Atom 330, 2GB RAM, 5400 RPM HDD, GNU/Linux