if we do any modifications or if we add any image in tm_slider block and click on save button it is taking much time and getting 504 gateway time error and website is also not working 10 t0 15 mins at this time and when i check in system log i am getting below errors
[2019-05-28 16:15:33] main.ERROR: Unable to resolve the source file for 'adminhtml/Magento/backend/en_US/images/5percentoffer.png' [] []
[2019-05-28 16:15:33] main.CRITICAL: Unable to resolve the source file for 'adminhtml/Magento/backend/en_US/images/5percentoffer.png' [] []
[2019-05-28 16:15:33] main.ERROR: Unable to resolve the source file for 'adminhtml/Magento/backend/en_US/images/banner5.png' [] []
[2019-05-28 16:15:33] main.CRITICAL: Unable to resolve the source file for 'adminhtml/Magento/backend/en_US/images/banner5.png' [] []
[2019-05-28 16:15:36] main.ERROR: Unable to resolve the source file for 'adminhtml/Magento/backend/en_US/images/main-banner.jpg' [] []
[2019-05-28 16:15:36] main.CRITICAL: Unable to resolve the source file for 'adminhtml/Magento/backend/en_US/images/main-banner.jpg' [] []
[2019-05-28 16:15:38] main.ERROR: Unable to resolve the source file for 'adminhtml/Magento/backend/en_US/images/5percentoffer.png' [] []
[2019-05-28 16:15:38] main.CRITICAL: Unable to resolve the source file for 'adminhtml/Magento/backend/en_US/images/5percentoffer.png' [] []
[2019-05-28 16:15:41] main.ERROR: Unable to resolve the source file for 'adminhtml/Magento/backend/en_US/images/banner2.jpg' [] []
[2019-05-28 16:15:41] main.CRITICAL: Unable to resolve the source file for 'adminhtml/Magento/backend/en_US/images/banner2.jpg' [] []
[2019-05-28 16:15:41] main.ERROR: Unable to resolve the source file for 'adminhtml/Magento/backend/en_US/images/banner2.jpg' [] []
[2019-05-28 16:15:41] main.CRITICAL: Unable to resolve the source file for 'adminhtml/Magento/backend/en_US/images/banner2.jpg' [] []
[2019-05-28 16:15:42] main.ERROR: Unable to resolve the source file for 'adminhtml/Magento/backend/en_US/images/banner5.png' [] []
[2019-05-28 16:15:42] main.CRITICAL: Unable to resolve the source file for 'adminhtml/Magento/backend/en_US/images/banner5.png' [] []
I have a same issue