I've created a 50 GB mp4 file (full HD) from a WLMP project that took me days to complete due to all of the bugs in Windows Movie Maker 2012 (build 16.4.3528.0331). Now, after hours of rendering, the file won't play. Not in Windows Media Player, not in VLC.

So I Googled it, and it seems that this issue was reported years ago, and Microsoft promised to solve it (see this post). According to Microsoft (see the same post), the issue has to do with the file size, which apparently is limited to 4 GB (!?!?!?!). 4 GB equals 23 minutes of video in full HD. Quite funny, since Movie Maker is supposed to make movies... and what movie is shorter than 23 minutes? So Microsoft, when are you going to address this issue?!

While you are at it, please make sure that texts and audio files stay in place (relative to the video clips they belong to) when projects are edited and/or saved and re-opened. Right now, texts and audio continuously move around, making it impossible to create movies at all.