DS1307 i2c problems with Uno WiFi Rev2

Projects Networking, Protocols, and Devices
1

I am having a little trouble with connecting the DS1307 module, by elegoo, with my Uno WiFi Rev2. I could easily connect it with my NodeMCU over i2c and can verify that the module works. I also was able to connect a bme280 with my Uno WiFi Rev2 and it was connected just fine.
But somehow when I connect the DS1307 with the Uno WiFi Rev2 it doesn't get detected by the i2c Scanner.
Of course, just like with the BME280, I connected VCC to 5V, GND to GND, SCL to SCL and SDA to SDA.
The DS1307 even works while connected to the Arduino, as I were able to use the SQW signal at 1Hz to blink an LED.

Does anyone know why this won't work?

Edit: Just tried a 20x04 LCD Display and it was also detected by the i2c Scanner.

2

Check your 5V pin's voltage. Also check the voltage of the battery on the DS1307 module. What do you read?

If the Vcc of the DS1307 (attention: the chip, not the module, I have no clue what circuit your module has) drops below 1.25 * voltage of the battery it disables the I2C interface (but still works and does the rest of it's job).