Problem with sending packets through SSL connection

Hello, we are a school environment. Our financial department is using a software for sending employee salary declarations to outside server through SSL connection.
When they send 5 records (respectively 5 declarations) everything works well. But when they try to send 50 records after 30-40 sec. the software generate the following message: Connection timed out

I tested the same operation through VPN connection to a mate router and everything works well. But when I disconnected VPN the same situation. I tested the operation with another router (OpenWrt) without problems.

My setup is:
Mikrotik RouterBoard 2011UiAS (v 6.34.4)
TP-Link TL-SG2424

IP of the problem PC is 192.168.1.26

Firewall rules

0 XI  ;;; place hotspot rules here
      chain=unused-hs-chain action=passthrough log=no log-prefix="" 

 1    chain=input action=accept protocol=tcp src-address-list=web_and_winbox_access dst-port=8080 log=no log-prefix="" 

 2    chain=input action=accept protocol=tcp src-address-list=web_and_winbox_access dst-port=8291 log=no log-prefix="" 

 3    chain=input action=accept protocol=tcp dst-port=1723 log=no log-prefix="" 

 4    ;;; default configuration
      chain=input action=accept protocol=icmp log=no log-prefix="" 

 5    ;;; default configuration
      chain=input action=accept connection-state=established,related log=no log-prefix="" 

 6    ;;; default configuration
      chain=input action=drop in-interface=ether1-ISP log=no log-prefix="" 

 7    ;;; default configuration
      chain=forward action=accept connection-state=established,related log=no log-prefix="" 

 8    ;;; default configuration
      chain=forward action=drop connection-state=invalid log=no log-prefix="" 

 9    ;;; default configuration
      chain=forward action=drop connection-state=new connection-nat-state=!dstnat in-interface=ether1-ISP log=no log-prefix="" 

10    chain=forward action=drop src-address=192.168.1.0/24 dst-address=192.168.16.0/24 log=no log-prefix="" 

11    chain=forward action=drop src-address=192.168.16.0/24 dst-address=192.168.1.0/24 log=no log-prefix="" 

12    chain=forward action=drop src-address=192.168.3.0/24 dst-address=192.168.1.0/24 log=no log-prefix="" 

13    chain=forward action=drop src-address=192.168.1.0/24 dst-address=192.168.17.0/24 log=no log-prefix="" 

14    chain=forward action=drop src-address=192.168.17.0/24 dst-address=192.168.1.0/24 log=no log-prefix="" 

15    chain=forward action=drop src-address=192.168.1.0/24 dst-address=192.168.18.0/24 log=no log-prefix="" 

16    chain=forward action=drop src-address=192.168.18.0/24 dst-address=192.168.1.0/24 log=no log-prefix="" 

17    chain=forward action=drop src-address=192.168.10.0/23 dst-address=192.168.1.0/24 log=no log-prefix="" 

18    chain=forward action=drop src-address=192.168.10.0/23 dst-address=192.168.3.0/24 log=no log-prefix="" 

19    chain=forward action=drop src-address=192.168.10.0/23 dst-address=192.168.16.0/24 log=no log-prefix="" 

20    chain=forward action=drop src-address=192.168.10.0/23 dst-address=192.168.17.0/24 log=no log-prefix="" 

21    chain=forward action=drop src-address=192.168.10.0/23 dst-address=192.168.18.0/24 log=no log-prefix="" 

22    chain=forward action=drop src-address=10.10.10.0/24 dst-address=192.168.17.0/24 log=no log-prefix=""

Anyone?