Extreme lag when footage is on a server

Hello everyone,

I've been editing a lot of 4K .r3d files in the past few years. The files were stored on different external hard drives such as Areca and G-Speed Shuttle XL. These drives are in Raid 5 and have a Thunderbolt connection which are perfect for working in a 3 Camera Multicam sequences on Full playback quality without any lag.

Recently our company bought a server and I copied the 4K files on it. However, for some reason the Multicam videos now are like a photo slide show even on 1/8 playback quality. The lag is terrible even with a direct 10Gbps connection to the server. The Activity Monitor on the iMac Pro shows ~40-80 MB speed. I tried playing the same files in the QuickTime player and the result was totally different - six 4K files were playing at the same time without any lag and the Activity Monitor was indicating 600-800 MB speed. I tested the same thing on a Windows 10 machine but the results were the same - when several files are playing at the same time from a video player, there is absolutely no problem. But when I make a Multicam sequence in Premiere the playback is very slow even with maximum decreased playback quality.

Is there something in Premiere's settings that is causing this lag? I spent a lot of time browsing and trying to find a solution for this but no luck so far.

Please help!

Thank you!