flv audio stutters in VLC

[team mate]

Hello!

I have a lot of old flv videos, which I converted years ago, not knowing that flv is a bit of a crap format to store videos...

Anyways. They used to play fine in VLC. Now the audio stutters and the video rushes, so at the end, whilst the audio is still playing, the screen is black. They also don't play properly when I try chucking them into Chrome or Firefox.

However, the video plays fine in the Get FLV player.

This is the video info:

Type: Video
Codec: H264 - MPEG-4 AVC (part 10) (avc1)
Resolution: 512x386
Display resolution: 512x386
Frame rate: 25
Decoded format: Planar 4:2:0 YUV

Type: Audio
Codec: MPEG AAC Audio (mp4a)
Channels: Stereo
Sample rate: 44100 Hz

I tried converting them with freemake, but the MP4 plays just as weird. Because it's a lot of files, I don't wanna fix them all manually. Is there anything I can do that will make them play correctly, or any programme that can fix them in bulk?

Thanks in advance!