Hi Hossam Eldin,
Thank you for contacting Syncfusion support.
Based on your query “the application became extremely slow after less than 5 minute” we have prepared an sample and checked, but unfortunately we are unable able to replicate this issue in our sample. For further references please refer to the below sample and video.
If our replication procedure is differed from the actual procedure, please let us know and share some more information based on how you have customized the clock control in your sample or please modify the above sample in such a way that issue replicates, which will be helpful for us to let you know a solution ASAP.
Regards,
Anirudhan