1. Which version are you running (Help>About)?
2. Open the source file, click on Tools>Show Program info and using the copy button in the lower left paste that info into a reply. This will give us more info about the file.
3. You can try running Tools>QuickStream fix and see if that (a) runs quickly, and (b) cleans up the internals of the file to see if makes editing quicker.
4. Have you tried the V6 beta to see if that improves things?
v 5.4.84.771
(Here's a smaller one, just 3 files, joined)
btw, I cannot load these together using combine, only join
File: Name : A:\files\Jeopardy - 04-09-20 (02) (02).mp4
Size : 0.708 GB
Duration : 00:58:28.41
Mux type : MP4
Video: Encoding : H.264
VideoStreamID : x201
Frame rate : 59.94 fps
Encoding size : 1280 x 720
Aspect ratio : 16:9
Header bit rate : 20.000 Mbps
VBV buffer : 456 KBytes
Profile : Main/4.0
Progressive : Progressive
Chroma : 4:2:0
Entropy mode : CABAC
Bit rate : 1.549 Mbps
Captioning : None found
Audio Stream: 1 (Primary) Codec : AAC
Format : RAW
Channels : 2.0
Language : und
PID : x202
PES Stream Id : xC0
Sampling rate : 48000
quickstream fix doesn't change the performance
no, I haven't tried the v6 beta, I only have a license for v5
Here are 2 individual files I cannot combine (but can join)
File: Name : C:\Users\core5\AppData\Roaming\VideoReDo-TVSuite5\Jeopardy - 04-05-20 (05).VLST
Size : 0.252 GB
Duration : 00:19:24.09
Mux type : MP4
Video: Encoding : H.264
VideoStreamID : x201
Frame rate : 59.94 fps
Encoding size : 1280 x 720
Aspect ratio : 16:9
Header bit rate : 20.000 Mbps
VBV buffer : 456 KBytes
Profile : Main/4.0
Progressive : Progressive
Chroma : 4:2:0
Entropy mode : CABAC
Bit rate : 1.661 Mbps
Captioning : None found
Audio Stream: 1 (Primary) Codec : AAC
Format : RAW
Channels : 2.0
Language : und
PID : x202
PES Stream Id : xC0
Sampling rate : 48000
File: Name : C:\Users\core5\AppData\Roaming\VideoReDo-TVSuite5\Jeopardy - 04-08-20.VLST
Size : 0.243 GB
Duration : 00:19:32.07
Mux type : MP4
Video: Encoding : H.264
VideoStreamID : x201
Frame rate : 59.94 fps
Encoding size : 1280 x 720
Aspect ratio : 16:9
Header bit rate : 20.000 Mbps
VBV buffer : 456 KBytes
Profile : Main/4.0
Progressive : Progressive
Chroma : 4:2:0
Entropy mode : CABAC
Bit rate : 1.594 Mbps
Captioning : None found
Audio Stream: 1 (Primary) Codec : AAC
Format : RAW
Channels : 2.0
Language : und
PID : x202
PES Stream Id : xC0
Sampling rate : 48000