Distance fields not working in 4.17

Distance fields don’t seem to be working at all in 4.17. They work perfectly in 4.14 on the same machine.

In bothcases; enabled distance fields in the project settings and restarted. In 4.17 a default map says “generating distance fields (1)…” for a few seconds and no changes are visible. In 4.14 it says “generating distance fields (32)…” which ticks down as expected.

Enabling the Mesh Distance Field visualisation flag works as expected in 4.14 (switching to a black screen with white fog for the fields), but just makes the standard view slightly brighter in 4.17. Changing distance field resolution settings has no effect in 4.17 (I’d expect it to have to rebuild?)

I’ve tried enabling 8 bit DF more in 4.17 with no change there either.

Any tips? 'cos it looks like it might just be broken. I’d assume that this issue (or misunderstanding) was actually introduced in 4.16, when the extra DF settings were added.