Describe the problem

A ModbusRTU slave example using the ModbusRTUSlave library (by CMB27) stops responding to Modbus requests when compiled and uploaded using Arduino IDE 2.3.6. It works perfectly on IDE 2.3.2 using the exact same board and code.
This affects communication on boards like Uno, Nano, and Leonardo (AVR core 1.8.6). Likely a regression in serial/RS-485 handling introduced between IDE versions.
No error messages – just silent failure.

To reproduce

A ModbusRTU slave example using the ModbusRTUSlave library (by CMB27) stops responding to Modbus requests when compiled and uploaded using Arduino IDE 2.3.6. It works perfectly on IDE 2.3.2 using the exact same board and code.
This affects communication on boards like Uno, Nano, and Leonardo (AVR core 1.8.6). Likely a regression in serial/RS-485 handling introduced between IDE versions.
No error messages – just silent failure.

Expected behavior

pls solve this problem

Arduino IDE version

2.3.2 vs 2.3.6

Operating system

Windows

Operating system version

Windows 11

Additional context

No response

Issue checklist

• I searched for previous reports in the issue tracker
• I verified the problem still occurs when using the latest nightly build
• My report contains all necessary details