Thanks for reporting. This should now be fixed on the develop branch in commit 570323d.
The issue was introduced in commit b857f96 which replaced some (unsafe) calls to select() with poll() in response to this thread. However, as @samuel helpfully pointed out here, WSAPoll is buggy and fails to report failed connections causing an issue with the JUCE socket classes that are used under the hood in InterprocessConnection and causing the bug you mentioned. Unfortunately Windows have marked the WSAPoll bug as “won’t fix” so we can’t use it and need to revert back to select() instead.