Problems with location info on Mac mini photos

I have been using Photos library for a number of years. My 40,000 or so photos are on iCloud and also stored on my iMac 27 inch (late 2015 and also on my iPad and iPhone. Most of the photos were taken on iPhone (with geo-tags added automatically) ; many of other photos (on various cameras and digital cameras over time) were not geo-tagged at source (but this info I added manually into the metadata in many cases via Photos). I have never has problems with location info and could search by it on any of these platforms.

I purchased a Mac mini M4 a couple of weeks ago to replace my aging iMac. A great machine, however I have been running into problems with location info on my pictures on the Photos app on my new Mac mini. Specifically even though the metadata info shows the map and re pin which identifies the location, the text in the info pop up says “Looking up location info..” But this never gets resolved. Meantime on any other platform (including my old iMac which I have not retired yet) the location text information is there. What makes this strange is that n the Mac mini for some pictures it has the map with the “Looking up location info..” But with some photos it DOES have the location identified. For example, for a sequence of 6 photos taken within a few minutes of each other (at same location), 2 DO have location info identified in the text whereas 4 will have “Looking for location info..”. I have same issue with photos I had previously manually tagged (all will have the map and pin info but some will have “Looking up…” even though same location). In all cases when I check on any of the other platforms this problem does not exist. If I use the search field to search by location “London” it shows 75 pictures whereas if I use the Map it shows there are 1,696 pictures. 

I should add that after the first inconsistencies, I backed up the library on my Mac mini and redownloaded the whole library from scratch from iCloud. This did not fix the problem. (I previously tried running repair library). 

My hypothesis is this is something in the software on my new Mac mini. Currently running MacOS Sequoia 15.1, Photos 10.0 (711.0.180).  My old iMac is still on Monterey 12.7.6 and Photos 7.0.  Both machines are on same home network going through same router etc (in case any questions on access to apple server to resolve location info). And in both cases the photos library is on an external SSD connected to each respective (i)Mac (ie each has a dedicated SSD).

Any thoughts/suggestion are appreciated ! Thanks.