MicroG's latest version (0.2.7.17455) switched to Mapbox for map rendering. MicroG's implementation of Mapbox is currently buggy, although the performance is much improved. This version should have been marked as a preview release, in my view, since it's not stable enough for use.
Can you try the previous version (0.2.6.13280)? If you're using LineageOS for MicroG, the latest build on or before June 2 contains the previous version.