Table alters via update set sometimes do not invalidate cache correctly on other nodes. The table descriptor cache for the affected table must be invalidated manually in order to correct the issue. If the alter is a column creation, this can result in the column not being visible on some nodes. If the alter is a column drop, this can cause SQL syntax errors on some nodes such as the one below:

"Syntax Error or Access Rule Violation detected by database (Unknown column 'task0.u_sla_response' in 'field list')"

Any table-altering change committed via update set is susceptible to this issue. It seems to be correlated with user activity on other nodes at the time of the commit, but this is not confirmed.

Flush the table descriptor cache for the affected table by running this script from the Scripts - Background module:

GlideTableManager.invalidateTable('table_name');
GlideCacheManager.flushTable('table_name');

NOTE: As a last resort, you can use gs.invalidateCache(); but this will degrade performance on the instance.