Pokemon Go recently launched the Buddy Adventure feature which allows Buddy Pokemon to follow the trainer or character on the map. Players can use this new feature with AR+ mode on & without it. Niantic also launched Shared AR experiences.
However, many reports are suggesting that the Shared AR Experiences causes crashing on certain Devices. Well, Niantic has officially acknowledged the issue & has shared the Issue description along with its current status. Have a look at the official issue description down below.
Issue Description: Players using certain devices that support AR Core or AR Kit are unable to successfully access all features in Shared AR Experiences. This issue occurs because not all devices compatible with AR Core or AR Kit are compatible with Shared AR Experiences.
Issue Status: A small number of devices that meet the above criteria were individually marked as incompatible due to performance issues discovered in testing.
So, currently, there will be no fix from Niantic end if you are facing this issue. You need to have a phone which supports AR Core to use Shared AR Experiences.