Possible Bug - Frame gets stuck for remainder of video on export project ?

Not sure if anyone else has experienced this potential bug, but recently i've exported a couple of projects where the exported video will play fine till part way through, then suddenly for the remainder of the video will be stuck on a frame till the end of the video. Checking the timeline afterwards all the other clips are there fine and another export usually solves it.

Anyone else experienced this bug? Will probably report it to Apple as well, just curious to see if i'm the only one?

I've seen this when copying a clip from one project to another. Deleting the project render files fixed it.

I don't think i've copied any clips from one project to another, but will definitely try deleting the render files next time it happens. At least someone else has experienced it.

Please give complete specs of your video and audio and your project properties.

Not near the machine at the moment, but off the top of my head, video was originally shot on Canon 5D so H264 codec 1920 x 1080 25p, imported into FCPX then transcoded in FCPX with transcode to optimised media setting. Audio in the project is WAV with some graphics in animation codec with alpha channel.

Project property is 1920 x 1080 25p and i think audio is 48khz stereo.