MIDI file upload comes out strangely and incorrect

Upload? To musescore.com?
Or import? into MuseScore Studio?

MIDI is a coded representation of the playback of a piece for a particular instrument and does not directly translate back into sheet music without extra effort. This seems to be particularly true of slow, expressive pieces.

A MIDI file is basically a written set of instructions which tells a synthesizer how to play music.
Simply put, it relays a set of on/off pitch commands, along with numerical values for setting electronic switches.

Here's some music notation:

Notice especially the staccato quarter notes followed by one eighth-note and one eighth-rest.

Here's that notation as a MuseScore file (19.3 KB): Example.mscz

Here's the MIDI file (merely 189 bytes): Example.mid
...and, from that MIDI file, the MIDI event list (instructions to a synthesizer):

which totals 37 events. (Seven notes are played: 67, 71, 74,79, 74, 71, 67)

MuseScore employs over 200 lines of code for the same example. MuseScore must distinguish and differentiate whole//half/quarter/etc. notes, staccato, and a plethora of other elements -- measures, time/key signatures -- all of which is necessary to produce a printable score in agreement with generally accepted notation standards.

MIDI lacks important scoring details which MuseScore will generate, often requiring corrections in order to create a presentable score.
If you are trying to get music into MuseScore from another source, consider using MusicXML if available. It is a far better choice.