Most of the time the Merge Request --> Compare feature works fine, but for one particular branch of ours we get the “Something went wrong on our end” error message. Digging through logs I found this in /var/log/gitlab/gitlab-rails/production.log. Completed 500 Internal Server Error in 175ms (ActiveRecord: 23.5ms) ActionView::Template::Error (121…121 out of range): 1: - environment = local_assigns.fetch(:environment, nil) 2: - show_whitespace_toggle = local_assigns.fetch(:show_whitespace_toggle, true) 3: - can_create_note = !@diff_notes_disabled && can?(current_user, :create_note, diffs.project) 4: - diff_files = diffs.diff_files 5: - merge_request = local_assigns.fetch(:merge_request, false) 6: 7: .content-block.oneline-block.files-changed.diff-files-changed.js-diff-files-changed{ class: (“diff-files-changed-merge-request” if merge_request) } lib/gitlab/string_range_marker.rb:39:in []=' lib/gitlab/string_range_marker.rb:39:inblock in mark’ lib/gitlab/string_range_marker.rb:33:in each' lib/gitlab/string_range_marker.rb:33:ineach_with_index’ lib/gitlab/string_range_marker.rb:33:in mark' lib/gitlab/diff/inline_diff_marker.rb:5:inmark’ lib/gitlab/diff/highlight.rb:29:in block in highlight' lib/gitlab/diff/highlight.rb:21:inmap’ lib/gitlab/diff/highlight.rb:21:in with_index' lib/gitlab/diff/highlight.rb:21:inhighlight’ lib/gitlab/diff/file.rb:129:in highlighted_diff_lines' lib/gitlab/diff/file_collection/merge_request_diff.rb:52:incache_highlight!’ lib/gitlab/diff/file_collection/merge_request_diff.rb:28:in decorate_diff!' lib/gitlab/diff/file_collection/base.rb:25:inblock in diff_files’ lib/gitlab/git/diff_collection.rb:85:in block in decorate!' lib/gitlab/git/diff_collection.rb:150:inblock in each_rugged_patch’ lib/gitlab/git/diff_collection.rb:124:in each' lib/gitlab/git/diff_collection.rb:124:ineach_rugged_patch’ lib/gitlab/git/diff_collection.rb:49:in block in each' lib/gitlab/gitaly_client.rb:232:inblock (2 levels) in migrate’ lib/gitlab/gitaly_client.rb:274:in allow_n_plus_1_calls' lib/gitlab/gitaly_client.rb:227:inblock in migrate’ lib/gitlab/metrics/influx_db.rb:95:in measure' lib/gitlab/gitaly_client.rb:225:inmigrate’ lib/gitlab/git/diff_collection.rb:45:in each' lib/gitlab/git/diff_collection.rb:84:ineach_with_index’ lib/gitlab/git/diff_collection.rb:84:in decorate!' lib/gitlab/diff/file_collection/base.rb:25:indiff_files’ lib/gitlab/diff/file_collection/merge_request_diff.rb:16:in diff_files' app/views/projects/diffs/_diffs.html.haml:4:in_app_views_projects_diffs__diffs_html_haml___2936660900574289108_70293681188740’ app/views/projects/merge_requests/diffs/_diffs.html.haml:18:in _app_views_projects_merge_requests_diffs__diffs_html_haml___4299823640361657915_70293654431520' app/controllers/application_controller.rb:246:inview_to_html_string’ app/controllers/projects/merge_requests/diffs_controller.rb:14:in show' lib/gitlab/i18n.rb:47:inwith_locale’ lib/gitlab/i18n.rb:53:in with_user_locale' app/controllers/application_controller.rb:324:inset_locale’ lib/gitlab/middleware/multipart.rb:93:in call' lib/gitlab/request_profiler/middleware.rb:14:incall’ lib/gitlab/middleware/go.rb:18:in call' lib/gitlab/etag_caching/middleware.rb:11:incall’ lib/gitlab/middleware/read_only.rb:31:in call' lib/gitlab/request_context.rb:18:incall’ lib/gitlab/metrics/requests_rack_middleware.rb:27:in `call’