Two people updating the hours on a task at the same time?

Hello,

We experienced a big performance hit yesterday in one of our Outage projects, taking a very long time to schedule critical path.  It was discovered that two people were updating the hours on an activity at the same time during this time. One of the users locked up their session as well. Is this a known performance issue?  I understand the implications regarding data integrity e.g. their changes overwriting each other, but was wondering what the impact is on performance.

Thanks!