Thanks @OttoKerner !
I just uninstalled the app and deleted the whole AppData\Local\PlexMediaPlayer folder and that solved the problem.
For reference here are the content of my old plexmediaplayer.conf file
{
"sections": {
"appleremote": {
"emulatepht": true
},
"audio": {
"channels": "2.0",
"device": "auto",
"devicetype": "basic",
"exclusive": false,
"normalize": true,
"passthrough.ac3": false,
"passthrough.dts": false,
"passthrough.dts-hd": false,
"passthrough.eac3": false,
"passthrough.truehd": false
},
"cec": {
"activatesource": true,
"enable": true,
"hdmiport": 0,
"poweroffonstandby": false,
"suspendonstandby": false,
"usekeyupdown": false,
"verbose_logging": false
},
"main": {
"alwaysOnTop": false,
"automaticUpdates": true,
"clientUUID": "",
"disablemouse": false,
"forceAlwaysFS": false,
"forceFSScreen": "",
"fullscreen": true,
"hdmi_poweron": false,
"layout": "auto",
"logLevel": "debug",
"manualUpdateCheck": true,
"minimizeOnDefocus": false,
"preventSystemScreensaver": false,
"remoteInspector": false,
"sdlEnabled": true,
"showPowerOptions": true,
"updateChannel": 0,
"useHelper": true,
"useOpenGL": false,
"useSystemVideoCodecs": false,
"webMode": "desktop",
"webserverport": 32433
},
"manualServers": {
"ip1": "",
"ip2": "",
"port1": "32400",
"port2": "32400"
},
"openelec": {
"systemname": "PlexMediaPlayer"
},
"path": {
"helperprogram": "",
"startupurl_desktop": "bundled",
"startupurl_tv": "bundled"
},
"privacy": {
},
"subtitles": {
"color": "#EEEEEE,#000000",
"placement": "center,bottom",
"size": 32
},
"video": {
"aspect": "normal",
"audio_delay.24hz": 0,
"audio_delay.25hz": 0,
"audio_delay.50hz": 0,
"audio_delay.normal": 0,
"cache": 75,
"debug.force_vo": "",
"deinterlace": false,
"directPlay": true,
"directStream": true,
"hardwareDecoding": "disabled",
"refreshrate.auto_switch": false,
"refreshrate.avoid_25hz_30hz": false,
"refreshrate.delay": 3,
"sync_mode": "audio"
}
},
"version": 4
}