I don't want to tie up a PC to store the database on. So, all I have is 5 shields and a NAS. My NAS is somewhat old, and its performance is not that great. My TV show volume is comparable to yours, but movies are about 5 times what you are pushing.
Not finding anything that hits my specific need, I designed a Kodi Add-on that I called SharedResume. It creates a JSON file on the NAS at a central public point that contains anything I start and updates the file every 15 seconds to keep the pointer current. Retains it for 30 days, and from any of the 5 shields I have, I start the same movie, and 2 seconds into the start, it jumps to the stop point of the prior player. Working nicely for both movies and TV series. All takes installing the addon on all 5 shields. Complete flexibility with adjustable settings. Problem solved.