Exported file freezes

I experience very long export time for a 1hr 29mins movie but the real issue is the exported clip has multiple freezed frames. What could be causing this please. I use Beta version on Premiere pro 2024. Same issue happens on the 2024 version then i tried the Beta. Imac spec is 

3.8 GHz 8-Core Intel Core i7

AMD Radeon Pro 5500 XT 8 GB graphics

128 GB 2667 MHz DDR4 ram