When Map Image Services published to ArcGIS Enterprise by selecting Layer Drawing as 'Dynamically from data' in ArcGIS Pro are tried to be cached later with custom scales, some scales in the cache are missing and cannot be cached.

Workaround

1. Create a Tiling Schema in XML format for scales 500000, 400000, 300000, 250000, 150000, 100000, 75000, 50000, 25000, 10000 using the Generate Map Server Cache Tiling Schema tool in ArcGIS Pro.
2. Right-click on the layer group in the Content Pane and open the Share As Web Layer window.
3. In the Configuration tab of the Share As Web Layer window, check Using Tiles from a new cache.
4.  In the Tiling Schema section, select Tiling Schema File and find the XML created and click OK.
5.  In Levels of Detail, ensure all scales are selected.
6. In Options, ensure the Cache Automatically on the server is checked.
7. Select PNG32 as Image Format.
8. Analyse and Publish.
9. After the Publishing, the Caching process will start and successfully Cache for all 10 scales.

Steps to Reproduce