If you select an arc by mistake, you must stop then restart your current measurement or the results may not be correct.
An effective workaround is to measure shorter lengths and then export these length values to a .cvs file using the Tube Length Bill of Materials command. Use Excel to add up the data. Shorter measurement errors are more tolerable to redo (i.e., reselecting four or five arcs is more manageable than reselecting 50 arcs).
Because the Tube Length function depends on arc radii selections for its calculations, an arc radius must be selected within the bend itself; otherwise, measurement results will be inaccurate.