Is this an excessively large 'Lock' time and is it indicative of a problem?
So the elephant in the room. Is that wait time excessive?

The lock waits from the screenshot show 18,024,389 ms / sec as the recent (average) wait time over the last couple of minutes.  That means for every second of &quot;wall clock time,&quot; there are 18,000 seconds (5 hours?!) of lock waits accumulated by queries.  That's so tremendously bad that I wonder if it's just a bug in the Activity Monitor UI.
Depending on how many cores the server has, and how many queries are running concurrently, even the smaller number (2.5 seconds of lock waits per second of wall clock time) is not ideal.
Those waits could imply a blocking chain (you can use sp_WhoIsActive to identify the lead blocker and then try to fix why it's blocking everything).  Regardless, they can definitely contribute to these client side timeouts you've described - every second that a query waits on locks is a second that it's not making progress on the actual query being run.