MT5 Build 5505 – Optimization fails on Custom Symbols - ticks send error / history synchronization interrupted

[Ahmed Sabba]

Hello

I am experiencing a problem in MT5 Build 5505 after the update on 16 Jan 2026. The issue occurs **only with optimization of EAs on custom symbols**. Here are the details:

1. **MT5 Build:** 5505  

2. **Problem:** Optimization stops with errors:  

   - "ticks send error"  

   - "ticks synchronization interrupted"  

3. **Symbols affected:** Only Custom Symbols (EURUSD, USDJPY, others created as custom)  

4. **Tick data:** Downloaded and imported correctly  

5. **EAs tested:** Multiple EAs (all work fine on regular symbols)  

6. **Agents:** Multi-agent optimization tested  

7. **Steps already tried:**  

   - Reinstalled MT5  

   - Cleared cache  

   - Used only one agent  

   - Forward testing  

8. **Previous behavior:** Worked perfectly on builds before 16 Jan 2026  

Is this a known bug in Build 5505 affecting custom symbols optimization? Is there a workaround, or will it be fixed in an upcoming update?

[Ryan L Johnson]

Ahmed Sabba:

The issue occurs **only with optimization of EAs on custom symbols...

You'd have to post your EA code to get a 100% accurate answer.

Having said that, the general cause of your opening statement is failing to specify a separate tradable symbol (order handling) in the EA code where the EA is running on a custom symbol. 

[Vladislav Boyko]

Ryan L Johnson #:
You'd have to post your EA code to get a 100% accurate answer.

What is needed is a way to reproduce it, not necessarily their advisor code. If it can be reproduced using MT5's built-in EA, great.

I don't have enough experience to try to reproduce this. Let's wait for someone more qualified in this matter...

[Alain Verleyen]

Ahmed Sabba:

Hello

I am experiencing a problem in MT5 Build 5505 after the update on 16 Jan 2026. The issue occurs **only with optimization of EAs on custom symbols**. Here are the details:

1. **MT5 Build:** 5505  

2. **Problem:** Optimization stops with errors:  

   - "ticks send error"  

   - "ticks synchronization interrupted"  

3. **Symbols affected:** Only Custom Symbols (EURUSD, USDJPY, others created as custom)  

4. **Tick data:** Downloaded and imported correctly  

5. **EAs tested:** Multiple EAs (all work fine on regular symbols)  

6. **Agents:** Multi-agent optimization tested  

7. **Steps already tried:**  

   - Reinstalled MT5  

   - Cleared cache  

   - Used only one agent  

   - Forward testing  

8. **Previous behavior:** Worked perfectly on builds before 16 Jan 2026  

Is this a known bug in Build 5505 affecting custom symbols optimization? Is there a workaround, or will it be fixed in an upcoming update?

Please provide the full log file, not screenshots. 

[Ahmed Sabba]

Alain Verleyen #:
Please provide the full log file, not screenshots. 

Here is the log file

[Ahmed Sabba]

Ryan L Johnson #:

You'd have to post your EA code to get a 100% accurate answer.

Having said that, the general cause of your opening statement is failing to specify a separate tradable symbol (order handling) in the EA code where the EA is running on a custom symbol. 

 I know very well when an EA has a problem and when the terminal itself is causing it. This issue is clearly on MT5 Build 5505, not the EA.

Thanks!

[Alain Verleyen]

Ahmed Sabba #:

Here is the log file

Thanks. I will check and get back to you.

[Ahmed Sabba]

Alain Verleyen #:
Thanks. I will check and get back to you.

ok thank you

[Ahmed Sabba]

I have tested this build https://t.me/MT5Exe/6 that you uploaded earlier. Everything is working perfectly, except for an error occurring in build 5505.