ArcGIS Pro freezes when using Measure tool

Every time I finish measuring the length of a line feature (specifically 500 m sections of a river) using the Measure tool in the Map ribbon, ArcGIS Pro freezes up and the swirling blue lagging cursor appears next to my mouse cursor. It takes several minutes for it to recover and in the meantime, I cannot do anything whilst I wait, including using the ‘Clear Results’ eraser button.

The line features have a spatial index ‘FDO_Shape’

Attribute INdex: ‘FDO_OBJECTID’

Data type: File Geodatabase Feature Class

Feature Type: Simple

Geometry Type: Line

This is really affecting my workoutput and I think there must be a bug in the system affecting the Measure tool.

Can anyone help fix this issue so that I can use the Measure tool without it freezing up my project?