I'm sorry. We got off to a bumpy start, although I believe that the exact date (and time and place) is important in this case to successfully debunk or confirm the statements made.
To get started on this, I suggest that we separate the allegations by Borodai about the trip of 12 Malaysian experts into three parts :
1) When the team of 12 Malaysian experts "arrived near the village of Yasinovataya, their car was attacked from the air by a SU-25 of the Ukrainian air force", and
2) "on their way to Donetsk, they ended up under a Ukrainian GRAD shelling".
3) the reason that the Ukrainians did (1) and (2) is to "prevent the team from getting to the MH17 crash site".
Assuming that these three statements are a fair definition of the claim in this case, I'd like to start with a quick assessment :
Regarding (1) Borodai knows that there is no evidence to debunk (1), since it never happened. So we can never debunk it.
Regarding point (2), even if we showed proof that GRAD shelling of Donetsk on the 21st was actually done by Borodai's own forces then we still cannot even debunk point (2) because Borodai stated "on their way to" Donetsk, not "in" Donetsk. Besides, that shelling happened in the morning and the Malaysians arrived in the evening.
Regarding (3), note that Borodai does not say explicitly that "the reason".."was to prevent the team from getting to the MH17 crash site". That reason is only implied because of the prior statements he makes from the 19:00 mark. And both you and me fell for that.
The REAL reason that the 12 Malaysian experts went to Donetsk on the 21st was to obtain the MH17 flight recorders. Which they did, eventually, after hours of negotiations with ... Mr. Borodai himself...
Considering that Borodai did not provide ANY evidence to his statements, I would like to make a counter-statement that is sustained by the little evidence we have, and does not suffer from Borodai's implication of reason :
When the 12 Malaysian experts went to Donetsk on the 21st, they were neither targeted by a Ukrainian SU25 nor by Ukrainian GRADs, while Mr. Borodai's own pro-Russian forces fired GRAD missiles on civilian targets in Donetsk in the morning of the 21st, for which they promptly blamed the Ukrainians, while the Malaysian experts went to Donetsk to obtain the flight recorders for MH17, which they did after hours of negotiations providing undisclosed concessions to Mr. Borodai himself.
That should not be hard to debunk if it is not true.