Series Support for Pocketbook

Last year I bought a Pocketbook Inkpad 3 and overall its been pretty good, but one issue I'm having is the series support. I do use Calibre to manage my library and about 90% of the time when syncing from Calibre to the Inkpad it will pick up all the metadata just fine. But some books just don't work correctly on the device when it comes to series. For instance, I have one series that has 14 books in it but books 4-7 just refuse to show up as part of the series. In Calibre I've done everything that I can think of with the metadata but sometimes the Inkpad just refuses to recognize that books are part of a series. The books are on the device because I can see and read them if I sort by author, but if I sort by series books just don't appear. I've deleted the books from the device, from Calibre, re-added, adjusted metadata multiple times. I've looked at the .opf data, series all match. And its not just one series that I've had issues with; multiple series from multiple sources have done this.

I've noticed that other people have had this issue and every post I've seen seems to be with Pocketbook. So is this a Pocketbook issue? If it is is there another e-reader that has proper series support that people like?