diff --git a/src/backend/middlewares/RenderingMWs.ts b/src/backend/middlewares/RenderingMWs.ts
index 9f2636be..b48948cf 100644
--- a/src/backend/middlewares/RenderingMWs.ts
+++ b/src/backend/middlewares/RenderingMWs.ts
@@ -98,7 +98,7 @@ export class RenderingMWs {
         delete (err.details); // do not send back error object to the client side
 
         // hide error details for non developers
-        if (!(req.session.user && req.session.user.role >= UserRoles.Developer)) {
+        if (!(req.session && req.session.user && req.session.user.role >= UserRoles.Developer)) {
           delete (err.detailsStr);
         }
       }
diff --git a/src/common/Utils.ts b/src/common/Utils.ts
index 12cd8264..b42bacb7 100644
--- a/src/common/Utils.ts
+++ b/src/common/Utils.ts
@@ -106,7 +106,7 @@ export class Utils {
       .replace(new RegExp('/+', 'g'), '/');
   }
 
-  static concatUrls(...args: Array<string>): string {
+  static concatUrls(...args: string[]): string {
     let url = '';
     for (const item of args) {
       if (item === '' || typeof item === 'undefined') {
diff --git a/src/frontend/app/ui/gallery/Media.ts b/src/frontend/app/ui/gallery/Media.ts
index 007f06b2..c9f7b6de 100644
--- a/src/frontend/app/ui/gallery/Media.ts
+++ b/src/frontend/app/ui/gallery/Media.ts
@@ -1,7 +1,7 @@
 import {Utils} from '../../../../common/Utils';
 import {MediaIcon} from './MediaIcon';
 import {Config} from '../../../../common/config/public/Config';
-import {MediaBaseDTO, MediaDTO, MediaDTOUtils} from '../../../../common/entities/MediaDTO';
+import {MediaBaseDTO, MediaDTOUtils} from '../../../../common/entities/MediaDTO';
 
 export class Media extends MediaIcon {
 
@@ -54,8 +54,7 @@ export class Media extends MediaIcon {
   getReplacementThumbnailPath(): string {
     const size = this.getReplacementThumbnailSize();
     return Utils.concatUrls(Config.Client.urlBase,
-      '/api/gallery/content/',
-      this.media.directory.path, this.media.directory.name, this.media.name, 'thumbnail', size.toString());
+      '/api/gallery/content/', this.getRelativePath(), 'thumbnail', size.toString());
 
   }
 
@@ -66,8 +65,7 @@ export class Media extends MediaIcon {
   getThumbnailPath(): string {
     const size = this.getThumbnailSize();
     return Utils.concatUrls(Config.Client.urlBase,
-      '/api/gallery/content/',
-      this.media.directory.path, this.media.directory.name, this.media.name, 'thumbnail', size.toString());
+      '/api/gallery/content/', this.getRelativePath(), 'thumbnail', size.toString());
   }
 
 
diff --git a/src/frontend/app/ui/gallery/MediaIcon.ts b/src/frontend/app/ui/gallery/MediaIcon.ts
index 83634914..9f1bfc20 100644
--- a/src/frontend/app/ui/gallery/MediaIcon.ts
+++ b/src/frontend/app/ui/gallery/MediaIcon.ts
@@ -24,19 +24,25 @@ export class MediaIcon {
   }
 
   getRelativePath(): string {
-    return Utils.concatUrls(this.media.directory.path, this.media.directory.name, this.media.name);
+    return Utils.concatUrls(this.media.directory.path,
+      this.media.directory.name,
+      this.media.name)
+      // do not escape all urls with encodeURIComponent because that make the URL ugly and not needed
+      // do not escape before concatUrls as that would make prevent optimizations
+      .replace(new RegExp('%', 'g'), '%25') // order important
+      .replace(new RegExp('#', 'g'), '%23')
+      .replace(new RegExp('\\$', 'g'), '%24');
   }
 
   getIconPath(): string {
     return Utils.concatUrls(Config.Client.urlBase,
       '/api/gallery/content/',
-      this.media.directory.path, this.media.directory.name, this.media.name, 'icon');
+      this.getRelativePath(), 'icon');
   }
 
   getMediaPath(): string {
     return Utils.concatUrls(Config.Client.urlBase,
-      '/api/gallery/content/',
-      this.media.directory.path, this.media.directory.name, this.media.name);
+      '/api/gallery/content/', this.getRelativePath());
   }
 
   getBestFitMediaPath(): string {