50 fps clips and 25fps clips on a 25fps timeline - end result, a jittery video

Hello People,

I have this problem with premier pro ir simply on my understanding for long and it is driving me Insane for a while, internet does not give a straight answer or most advises are just to slowdown or confirm interpret footage to 25fps .

Well i use a DJI drone which shoots at 25 fps , i use my cannon camera to shoot ground shots at 50 fps. ( i mainly shoot travel videos) 20% of my clips are 25fps and 70% are 50fps and 10% are 50fps that have been slowed down by 50%)

while editing i use a 25fps timeline, therefore my output will be 25 fps as well, i do not want to interpret all the 50fps footage as it slows down all the clips, i just want to slow down only few clips not all, the remaining 50fps clips i want them to be in real time. so i have some real 25fps clips and some slowed down( interepreted to 25fps) 50fps clips, and some 50fps clips in real time ( most of these are i real time n and slowed down)

Now the challenge i face is when i output the video in 25fps, the video is jittery and not neat, i tried every solution on the internet. i tried optical flow, frame blending, and even the default setting, frame sampling. nothing works, the output is still jittery and its is annoying to the point where i want to cancel my premier pro subscribtion and try another editing software.

any input/advise on this will be highly appreciated. 

thanks in advance 

Francis