Exported slideshow has flickering transitions

Transitions are "Classic" with 'Dissolve'. There are 360 photos in the slideshow which is a lot but I have had no problem with similar numbers in the past. Slide duration is set at 6 sec. It is all saved to my boot drive which has 600+gb available. I do not think that memory is an issue. It appears to me that using "Classic" with "Dissolve" is an issue here. There is no problem using any of the other themes or methods of transision given that all other methods of transition do the same ie push the slide from one direction to another at your choice. As far as I can see the issue is using "Dissolve." There seems to be some problem with Apple's program which needs some fix. I notice other people have exactly the same problem.

Thanks for your suggestion and help in changing the transition speed. I did try that out and changed that speed but it didn't make any difference. Still flickers on transitions intermittently. I also note that if I play back the slide show in Preview in the Photos program it works perfectly so it appears that this issue occurs when exporting the slide show.

Thanks again Tony for your suggestion. I have already tried starting in Safe Mode, Restarting and making sure Time Machine and Energy Saver were turned off. None of that made any difference. I did notice that lengthening the Dissolve speed made a bit of difference in that there was less flickering. However in the end there was still flickering. Running out of ideas now!

Dissolve is the process of going from one slide to the other so only takes about a second. The speed is set so can't change it.