Multiple lights (6 seen) fading on and off (10s) forming multiple formations moving in all directions (not orbital) in stratosphere

Here, I am going to recount briefly the occurrence on the early morning of 8th August 2023. Am giving you the details so that you can work out if any stratospheric military exercises of some sort were happening. I understand these may be classified, however, I trust your discretion in giving me feedback which I would greatly be appreciative of.
I am an airline captain flying over 30yrs with 20000hrs in jet
Last Tuesday early morning we saw several 'stars' suddenly moving in formation forward and reverse, changing in brightness sometimes forming a 5 dot formation akin to dots on a dice or a 3 dot vertical formation with the center one ahead.
Our position on the flight path was over NW Tunisia/Algeria border heading East at 37000' and we saw them for 20 minutes initially appearing to our left, therefore Northward, higher than us near Ursa Major between stars Dubhe and Merak (see photo).
I took several photos and videos but the OnePlus 11G camera on video does not have night mode, so I took several in 5 second interval with long exposure. I will provide the photos when you contact me. A sequence can be built. Apologies for the image shake during long exposure.
The movements were visible with the naked eye. At first it looked like a satellite with such magnitude and orbit vector as the ISS. I have an app to track the ISS and checked it that it wasn't it.
I confirmed it wasn't a satellite when a second one, even brighter appeared but in a slightly different upward direction and faster speed. They fade out within 10 seconds. 6 are the amount we witnessed simultaneously moving in formation and breaking formation. The formation aspect of them do not therefore indicate that they were very far as otherwise the distance between them would be tens of miles. If they were naturally forming a formation that kept for up to 30 seconds then breaking, even moving in reverse, then it may mean that the objects were far closer. No size could be determined. The colour was the colour of stars but occasionally brighter and bluer
I am also familiar with Iridium flashes as I follow them, but these were objects that reappear on and off and change direction albeit not sharply - First they fade then they appear in a different direction. This continued for approx 20 minutes at which point we started our descent and lost sight at around 20000' due to the haze but I could still make out one that shone brighter.
That is my account. My First Officer witnessed everything and I got the Cabin Manager to witness the event too.
I have about 130 sequenced low light shots. The photos are raw files with the full EXIF data attached. The 10 videos are not of much use. The flightdeck was turned very dark from an hour before the first sighting. The sightings are external and not window reflections except for large faint red blotches on pics being the reflection of my shirt in low light. They are not Starlink, satellites, space debris or Iridium flashes.
What got me concerned is the persistence of the sightings. When were descending through 25000' they actually appeared higher. That alone may signify the objects were closer.
This is the second similar occurrence seen, the other being earlier this year at night just south of Cyprus with 4 objects, some becoming very bright (brighter than Venus) before fading moving in different directions lasting about 15 minutes in total. They seemed to be much farther away this Tuesday's objects because they moved slower but were much higher.
The full set of images amount to 207Mb without the videos. I am willing to share the sequence through WeTransfer