Not long ago I updated ArcGIS to version 10.8 and found some major improvements in Spatial Analyst tools. For example in version 10.5 I struggled to compute Cost Back Link for large rasters due to memory error. It works now and it's very fast. Unfortunately there are some bad flaws.
Attached picture shows tiny extract from Cost Distance surface and one out of 6500 sources. Source point labelled by value sampled from Distance surface. This means that cost path exists between this point and some destination cell.
Picture also show 2 gaps in Distance surface (same is true for Back Link surface), as a result ArcGIS fails to complete Cost Paths. It gets to the stage "Tracing Cost Paths...", shows progress bar and nothing is happening afterwards. The longest I waited was 30 minutes before killing the process. I am able to isolate very few sources (3 out of 6500 in this case) and find cost paths from them, but a) this is a pain, because it involves some map algebra on big rasters and b) Cost Path tool that worked like a charm on any size surfaces in version 10.5 is so slow now that I was forced to develop my own tracing script that read-write from/to binary floating-point files.
I found that there are only 13 cells with missing values over a huge 25194*26924 cost raster and I can semi-manually fix it, but it is not how it should be.
Are you aware of patch fix for that?
If not I hope this post will get to ESRI developers.