ProgrammingATMEGA328p 1.8V using ftdi module 3.3V

hello everyone, I have flashed my atmega328p to work with 4Mhz and 1.8V but when I want to download my sketch, It does'nt work at 1.8V but it works when I supply my MCU at 1.85 V. Do you think it's because of the voltage difference between the module and the MCU ?
Thank you have a good day !

I can program it using VCC of the FTDI module then go to 1.8V and it works.

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