Crash during recording

Audicity 2.3.3 on Mac OS X 10.12.6 Sierra on iMac (21.5-inch, Mid 2011, iMac12,1) Processor: 2.5 GHz Intel Core i5; Memory: 4GB; Graphics: AMD Radeon HD 6750M 512 MB
Hard Drive: Mac OS Extended (Journaled), Capacity: 499.23 GB, Available: 438.23 GB

I am recording from line-in. After about an hour Audacity crashes with error:

Internal Error
Internal error at Project.cpp line 156.
Please inform the Audacity team at

I have plenty of hard drive space. This error just started cropping up. It won’t let me save even the hour’s recording most of the time. I have successfully recorded for 12+ hours in the last month with the same equipment and configuration. At one point recently I did try to save a project, but I erased that data and quit trying that. I have Audacity set to 32 KHz sample rate Mono.

I’m not sure what other information is relevant.