Git Mergetool error (Unexpected character b on line 1) and Hangs

After committing locally, I pull to the branch I got with conflicts, I run mergetool. After the first merge with opendiff, the terminal just hangs with the following error message:

FileMerge [1216: 43748] Failed to load "/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/Library/Xcode/Specifications/Core Build System.xcspec. Cause: Domain Error = NSCocoaErrorDomain Code = 3840 "Unexpected character b on line 1" UserInfo = {NSDebugDescription = Unexpected character b on line 1, kCFPropertyListOldStyleParsingError = Domain error = NSCocoaErrorDomain Code = 3840 "Unexpected"; or '=' after the key on line 1 "UserInnexfo = {NSDebugDescription ' ; ' or '=' after pressing the key on line 1}}. 2017-03-31 11: 32: 22.402 FileMerge [1216: 43748] Failed to load "/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/Library/Xcode/Specifications/Native Build System.xcspec . Reason:Domain Error = NSCocoaErrorDomain Code = 3840 "Unexpected character b on line 1" UserInfo = {NSDebugDescription = Unexpected character b on line 1, kCFPropertyListOldStyleParsingError = Domain error = NSCocoaErrorDomain Code = 3840 "Unexpected"; or '=' after the key in line 1 "UserInfo = {NSDebugDescription = Unexpected ';' or '=' after pressing the key on line 1}}.

There was no choice to open the project and manually check each conflict. O_O

Does anyone know what the problem is and how to fix this? Launching XCode 8.2.1. On a native iOS project with cocoapods installed.