The following issues are mentioned in the third beta's announcement:

• The Windows binaries of this third beta were compiled without enabling multiple threads (i.e., parallel processing with multiple cores).
• CSOLNP can still crash or freeze up R, or terminate calculation prematurely, when calculating confidence intervals. This behavior appears to be Windows-specific, and almost entirely confined to 64-bit R.
• Users should get into the habit of ALWAYS using the $ accessor instead of the @ accessor. For example, myModelRun@output$estimate would now be myModelRun$output$estimate. We CANNOT guarantee that every usage of the @ accessor that worked with versions 1.3/1.4 will continue to work in 2.0.

In addition, users have reported the following:

• CSOLNP is still producing confidence intervals that have a confidence limit equal to the point estimate [5] more frequently than it should.