Rider does not open the merge conflict window on large files

I am trying to resolve a merge conflict in Rider using "Git > Resolve Conflicts...". When selecting the file and clicking "Merge...", a window titled "Loading Revisions..." appears for a few seconds, then disappears. What is expected to happen next is a window that shows the selected file in its current version (left), server version (right) and resolve/work version (middle), but that window never appears.

This has happened to me on several Unity projects when attempting to resolve conflicts on large (10k+ lines) .prefab and .unity files. My PC has 16GB of ram, Rider is using 2GB and Rider Backend is using 1.1GB.

I have found this in frontend.log of Rider, which may or may not be relevant :

09:28:14.932 | INFO | GitMergeUtil | Couldn't resolve the MERGE_HEAD in file://C:/path/to/project: bad revision 'MERGE_HEAD'
09:28:15.032 | INFO | GitMergeUtil | Couldn't resolve the CHERRY_PICK_HEAD in file://C:/path/to/project: bad revision 'CHERRY_PICK_HEAD'
09:28:16.303 | DEBUG | RiderReloadVetoer | mayReloadFileContent for file://C:/path/to/conflicted/file.prefab
09:28:16.303 | DEBUG | RiderReloadVetoer | isUnderBackendCommand = false
09:28:16.303 | DEBUG | RiderReloadVetoer | isDocumentLoading = false