Issues with render video - Small file size after render.

Hello,
I recently started having the same problem on both of my work PCs. With the new version (later also on the older version) of Premiere Pro/Media Encoder, it means that, as always, I import the MP4 H265 video, import the intro and everything necessary. Subsequently, I also render the video in H265 1080p_25fps_3.5Mbps/ H265 2160p_50fps_7.5Mbps. But the problem arose when the render was completed to 100% and the resulting file, despite its length of e.g. 45 min, was only 24 bits (file size) and only when I render to MP4, when I render to AVI, the video is rendered but choppy but whole. Does anyone have the same problem?? Thanks for reply and helping