UPDATE: IMET78754 Radiosonde observed on APRS-fi and tracked on the Internet.

(Click on images for larger view.)

Here are some more information that I gathered iro IMET78754.  First observed position (-33.97712, 18.59984 @ 212m 24 December 2021, T 11.42.28  000000Z by ZS1AEG.

The balloon burst at 22 380 meters altitude on the 24 December 2021 at 14h38 SAST.