If I use Picard v2.1.3 to retrieve metadata, the URL in the opened Browser looks like this 

http://192.168.1.61:5000/taglookup?artist=Various%20Artists&release=Time-Life%20AM%20Gold%201963&track=&tracknum=&duration=&filename=&tport=8000

This search ends in a error like

Oops, something went wrong!

Error message: (No details about this error are available)

Time: 2019-08-15 16:56:17 UTC

Host: 72e66089454d

Interface language: en

URL: http://192.168.1.61:5000/taglookup?artist=Various%20Artists&release=Time-Life%20AM%20Gold%201963&track=&tracknum=&duration=&filename=&tport=8000

Request data:

$VAR1 = {
'body_parameters' => {},
'query_parameters' =>
Unknown macro: { 'track' => '', 'duration' => '', 'artist' => 'Various Artists', 'filename' => '', 'tracknum' => '', 'release' => 'Time-Life AM Gold 1963', 'tport' => '8000' }
};

We're terribly sorry for this problem. Please wait a few minutes and repeat your request — the problem may go away.

If I use my local MB server GUI, go to the search GUI (http://192.168.1.61:5000/search) and enter 2 search texts like

Various Artists

Time-Life AM Gold 1963

I get the same error as above.

But the URL from the GUI looks like:

http://192.168.1.61:5000/taglookup?tag-lookup.artist=Various+Artists&tag-lookup.release=Time-Life+AM+Gold+1963&tag-lookup.tracknum=&tag-lookup.track=&tag-lookup.duration=&tag-lookup.filename=

It seems that the single search-tokens are prefixed with tag-lookup.

I'm not sure if this could be one of the reasons, why the result is in both cases are the above error.

If I only use 1 search text ("Various Artists" OR "Time-Life AM Gold 1963") the page responds without error.

Do we have any limit in search combinations?