Indeed the timeout of the convert operation is set to 90 minutes. Just as you have noted, I also believe this is preventing you from converting the dump file into a JustTrace snapshot. We had a discussion in the team about this and we decided to completely remove the timeout. This will allow our users to wait for the process to complete as long as it's needed. The above change will be available in our next public release. Most probably, next week. So, stay tuned.
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