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The thing sticking out on top could be a rifle or antenna from a military backpack radio. If there is one person on the left there might as well be one on the right:

Silhouette resembling a soldier/S

The area looks like a beach with something like marram grass:

smoke/_

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The area looks like a beach with something like marram grass:

smoke/

S

+ŠD PČ OZN

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When stabilizing the whole scene, certain dark smudges turn out to be additional smoke and shadows casted by the plumes:

Smoke plumes rising vertically
Shadow of vertical smoke plumes cast on the UFO
Shadow of vertical smoke plumes cast on the ground

Around the alien seem to be footprints coming from the direction of the UFO behind, telling the story that the alien climbed out of the wreckage, managed to walk away but eventually collapsed:

/S´´KL

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Straightening the rig reveals full body proportions:

u/rorz_1978 was first to suggest utilizing the lower left leg from this scene to derive proportions./S/

Lining up every extraterrestrial being we see across Ivans videos suggests that they are either identical or at least of the same "alien race", as their proportions match:

Artistic completion of the legs based on straightened 3D model//////////S/

As both results are estimations we conclude by interpre/_O POČ / BYLO IKDYŽ NEŠ _ VISSSSSSSSSSSSSSSSSSS

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Applying u/RedDwarfBees panorama idea to the first autopsy scene reveals the corpse as a whole:

There is a dark spot on the glove the physician is wearing on his left hand. One single frame is focused just right to reveal more details:

It could be random stains or perhaps two digits resembling the number 98. In case of the latter, the (right-handed?) physician might have scribbled a measurement on his glove./S

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Symmetrical specular highlights stable across multiple frames

Especially the side-view suggests that the alien has either large,/S

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Straight segment as primary shadow indicator
Shadow wrapping around cheekbone into depression below the eye/