[Milhouse]

@cabrio: There's another possible explanation:

text:
2018-04-23 21:43:16.310119:Thread-1  : preparedl.JSON WEB REQUEST: [POST] [{"method": "Files.PrepareDownload", "params": {"path": "image://https%3a%2f%2fassets.fanart.tv%2ffanart%2fmovies%2f23398%2fmoviebanner%2falvin-and-the-chipmunks-the-squeakquel-53f60665859d9.jpg/"}, "jsonrpc": "2.0", "id": "preparedl"}]

2018-04-23 21:43:21.312405:Thread-1  : ** iotimeout occurred during web request **

2018-04-23 21:43:21.312405:Thread-1  : preparedl.RECEIVED WEB DATA: 408, Request Timeout, 

The iotimeout error (which I haven't seen for a long time) might suggest a problem/bug with your Kodi client, so check your Kodi log for errors.

Edit: It's likely the misbehaving fanart.tv website is causing Kodi to take longer than the 5 second communication timeout when the script requests information from Kodi, resulting in the iotimeout error (unfortunately this particular timeout is not configurable). You can try adding an increased timeout with the following patch:

text:
diff --git a/texturecache.py b/texturecache.py

index 820526e..983e3de 100755

--- a/texturecache.py

+++ b/texturecache.py

@@ -2759,7 +2759,7 @@ class MyJSONComms(object):

     REQUEST = {"method":"Files.PrepareDownload",

                "params":{"path": filename}}



-    data = self.sendJSON(REQUEST, "preparedl")

+    data = self.sendJSON(REQUEST, "preparedl", timeout=15.0)



     if "result" in data:

       return "/%s" % data["result"]["details"]["path"]