Took the CSV file FR24 published on their site and graphed the altitude as reported by the stations.
The results are below:
KGL9268 Altitude data - Album on Imgur
Whatever happened started some 255 seconds from the start of the published log, upto that point the aircraft was climbing normally and all stations were reporting consistent data. After that it gets fuzzy. The album also contains 4 more images - one is all altitude data after the 250. second and the rest is altitude data after the 250. second separated by station ID.
No interpretation from my side, thought it might come handy to someone.