Hi gurus !!
Check if you have any error in the SQL Server Errologs related with avaliable workers and raise the value in case you find this error.
How many databases you have using AlwaysON ? I plan tor prepare an 5000 databases AlwaysOn setup and my first tests ended with a bad result due a lack of threads. I increased the maximum workers value and it didn't help. Any of you have any experience with this amount of databases ? My understand is that it won't work with the hardware I have avaliable ( Two 16 corees 65 Gb of RAM ).
Check this table (The number of workers might vary depending the number of cores you have).