Hi Damien, 

I believe you will find what you're looking for in the Source Code of #Object#TimelineEntity 

e.g. for Activities in "ActivityTimelineEntity "

(...)
"TimelineEntityValues": [
         {
           "UId": null,
           "TypeColumnValue": "e2831dec-cfc0-df11-b00f-001d60e938c6",
           "IsDefault": true,
           "ComparisonType": 3,
           "TileName": "Email",
           "SortColumn": "SendDate",
           "OwnerColumn": "SenderContact",
           "IconId": null,
           "ColumnLayouts": [
             {
               "ColumnName": "Title",
               "ColumnLayout": "{\"column\": 1,\"row\": 1,\"colSpan\": 12,\"rowSpan\": 1}"
             },
             {
               "ColumnName": "Body",
               "ColumnLayout": "{\"column\": 1,\"row\": 2,\"colSpan\": 12,\"rowSpan\": 2}"
             }
           ]
         },
         {
           "UId": null,
           "TypeColumnValue": "e2831dec-cfc0-df11-b00f-001d60e938c6",
           "IsDefault": true,
           "ComparisonType": 4,
           "TileName": "Activity",
           "SortColumn": null,
           "OwnerColumn": "Owner",
           "IconId": null,
           "ColumnLayouts": [
             {
               "ColumnName": "Title",
               "ColumnLayout": null
             },
             {
               "ColumnName": "Status",
               "ColumnLayout": "{\"column\": 1,\"row\": 1,\"colSpan\": 6,\"rowSpan\": 1}"
             },
             {
               "ColumnName": "DetailedResult",
               "ColumnLayout": "{\"column\": 1,\"row\": 2,\"colSpan\": 6,\"rowSpan\": 1}"
             }
           ]
         }
       ]

I've not noticed that, at least not yet - although not really paid attention to any dashboards/charts/etc. If you look at the network requests in dev tools, do you see any requests in red (likely a SelectQuery) that might shed some light on what is causing the error?

They don't as far as I've found with a few cases of wanting archiving unfortunately.

I've always had to do some workaround such as copying the data using automated SQL scripts into an exact copy of the object for archiving purposes (I have done this by creating a new Object and setting its parent to the Object that needs archiving). This has some downsides that any changes to the regular Object won't apply to the archive Object until you re-publish the archive Object, so something to look out for.

Another issue to watch out for is how the archived data references other data, e.g. if you have parent-child relationships and you are archiving by copying exactly using SQL, the archived record would still be pointing at a "live" record rather than an archived one. Again, custom solutions are required for this.

Overall it's quite a pain, and plenty of issues can arise. It would be great if there were a built in way of doing so.