I have my media shared locally from a NAS with SMB. When Infuse is started fresh and the NAS is either turned off or the device is not in the same network (either cellular or a different LAN) artwork for library entries is not shown. Connecting to the WiFi and reloading any screen in Infuse will make it reload all the artwork. Most of the posters in my library are saved as jpg next to the video file but it also happens with the fanart backdrops.
Here is a video of what it looks like: https://streamable.com/9mm9b4
This bug has existed in the past, was fixed but was reintroduced in a recent update. This is on version 6.5