Phonetrack causes extremely high CPU load and lagging in different browsers

Hello,

I am running Phonetrack 0.2.8 on Nextcloud 13.0.2 with two sessions currently. Most of the time I open Phonetrack the browser gets extremely lagging and the CPU load gets extremely high. I can reproduce this on Firefox 57-62, Vivaldi, Chrome etc.

Here is a screenshot of Firefox Nightly (which shows the console window not opening):

I got the following error message:

Error: Script terminated by timeout at: w@https://1.1.1.1/apps/phonetrack/js/leaflet.js?v=b7771739-1:5:2186 _setPosition@https://1.1.1.1/apps/phonetrack/js/leaflet.js?v=b7771739-1:5:95807 _updatePosition@https://1.1.1.1/apps/phonetrack/js/leaflet.js?v=b7771739-1:5:96357 fire@https://1.1.1.1/apps/phonetrack/js/leaflet.js?v=b7771739-1:5:16616 _move@https://1.1.1.1/apps/phonetrack/js/leaflet.js?v=b7771739-1:5:41854 _onZoomTransitionEnd@https://1.1.1.1/apps/phonetrack/js/leaflet.js?v=b7771739-1:5:48577 _createAnimProxy/<@https://1.1.1.1/apps/phonetrack/js/leaflet.js?v=b7771739-1:5:47267 fire@https://1.1.1.1/apps/phonetrack/js/leaflet.js?v=b7771739-1:5:16616 _animateZoom@https://1.1.1.1/apps/phonetrack/js/leaflet.js?v=b7771739-1:5:48344 _tryAnimatedZoom/<@https://1.1.1.1/apps/phonetrack/js/leaflet.js?v=b7771739-1:5:48129 FrameRequestCallback*f@https://1.1.1.1/apps/phonetrack/js/leaflet.js?v=b7771739-1:5:1740 _tryAnimatedZoom@https://1.1.1.1/apps/phonetrack/js/leaflet.js?v=b7771739-1:5:48116 setView@https://1.1.1.1/apps/phonetrack/js/leaflet.js?v=b7771739-1:5:30236 fitBounds@https://1.1.1.1/apps/phonetrack/js/leaflet.js?v=b7771739-1:5:31505 zoomOnDisplayedMarkers@https://1.1.1.1/apps/phonetrack/js/phonetrack.js?v=b7771739-1:3538:13 displayNewPoints@https://1.1.1.1/apps/phonetrack/js/phonetrack.js?v=b7771739-1:2401:13 refresh/phonetrack.currentRefreshAjax<@https://1.1.1.1/apps/phonetrack/js/phonetrack.js?v=b7771739-1:1863:17 j@https://1.1.1.1/core/vendor/core.js?v=b7771739-1:2:26920 fireWith@https://1.1.1.1/core/vendor/core.js?v=b7771739-1:2:27738 x@https://1.1.1.1/core/vendor/core.js?v=b7771739-1:4:11251 b/<@https://1.1.1.1/core/vendor/core.js?v=b7771739-1:4:14765 EventHandlerNonNull*send@https://1.1.1.1/core/vendor/core.js?v=b7771739-1:4:14903 ajax@https://1.1.1.1/core/vendor/core.js?v=b7771739-1:4:10710 refresh@https://1.1.1.1/apps/phonetrack/js/phonetrack.js?v=b7771739-1:1846:45 getSessions/<@https://1.1.1.1/apps/phonetrack/js/phonetrack.js?v=b7771739-1:1810:13 j@https://1.1.1.1/core/vendor/core.js?v=b7771739-1:2:26920 fireWith@https://1.1.1.1/core/vendor/core.js?v=b7771739-1:2:27738 x@https://1.1.1.1/core/vendor/core.js?v=b7771739-1:4:11251 b/<@https://1.1.1.1/core/vendor/core.js?v=b7771739-1:4:14765 EventHandlerNonNull*send@https://1.1.1.1/core/vendor/core.js?v=b7771739-1:4:14903 ajax@https://1.1.1.1/core/vendor/core.js?v=b7771739-1:4:10710 getSessions@https://1.1.1.1/apps/phonetrack/js/phonetrack.js?v=b7771739-1:1760:9 main@https://1.1.1.1/apps/phonetrack/js/phonetrack.js?v=b7771739-1:5409:13 restoreOptions/<@https://1.1.1.1/apps/phonetrack/js/phonetrack.js?v=b7771739-1:1104:13 j@https://1.1.1.1/core/vendor/core.js?v=b7771739-1:2:26920 fireWith@https://1.1.1.1/core/vendor/core.js?v=b7771739-1:2:27738 x@https://1.1.1.1/core/vendor/core.js?v=b7771739-1:4:11251 b/<@https://1.1.1.1/core/vendor/core.js?v=b7771739-1:4:14765 EventHandlerNonNull*send@https://1.1.1.1/core/vendor/core.js?v=b7771739-1:4:14903 ajax@https://1.1.1.1/core/vendor/core.js?v=b7771739-1:4:10710 restoreOptions@https://1.1.1.1/apps/phonetrack/js/phonetrack.js?v=b7771739-1:985:9 @https://1.1.1.1/apps/phonetrack/js/phonetrack.js?v=b7771739-1:4314:13 j@https://1.1.1.1/core/vendor/core.js?v=b7771739-1:2:26920 fireWith@https://1.1.1.1/core/vendor/core.js?v=b7771739-1:2:27738 ready@https://1.1.1.1/core/vendor/core.js?v=b7771739-1:2:29530 I@https://1.1.1.1/core/vendor/core.js?v=b7771739-1:2:29721 EventListener.handleEvent*n.ready.promise@https://1.1.1.1/core/vendor/core.js?v=b7771739-1:2:29832 @https://1.1.1.1/core/vendor/core.js?v=b7771739-1:2:29924 @https://1.1.1.1/core/vendor/core.js?v=b7771739-1:2:207 @https://1.1.1.1/core/vendor/core.js?v=b7771739-1:2:2