SSD 1306 I2C OLED display: anyone else having trouble with one of these?

I recently bought a handful of these

to play with. So far I'm quite puzzled/disappointed by the result. They seem to work (that is, to be found by an I2C Scanner sketch) just once. After that, any attempt to talk on the I2C bus with this device attached will hang on endTransmission, so I2C_Scanner won't work any more. If I disconnect the device, I2C Scanner starts working again. But the device never works again.

I fear I may be killing them somehow, but can't figure out what I might be doing wrong. I've used a number of other IIC devices successfully, so it's not my first time connecting SDA and SCL :-)

I have tried powering the OLED from the Arduino, and also powering it independently (with a bboard power supply); I've put 4.7K pullups on SDA and SCL. Nothing seems to help. Before investing hours in a big debugging drama, I was wondering whether I've just bought a bum product and no one is having any joy with these devices.

I note that when I2C Scanner did work, it found the device at 0x3D; but the stencil on the module says it should be found at 0x78. This wasn't too reassuring re quality control :-)

Anyway, if anyone else has bought one of these and either found out how to make it work, or gave up and threw it away, I'd like to know :-)

Looks exactly like the one I bought on eBay.

my post about my display which is the same as yours

Thanks ieee48. I updated that thread with yet another library alternative, in case someone comes along later with a similar question. I'm using

which is quite current (Adafruit lib is about 2 yrs old now) and it seems to work OK so far. Author claims that his version of the SSD1306 lib is very miserly with resources and can be used on small controllers.

My original problem, amazingly, turned out to be the Arduino itself. Embarrassing. I have become a little complacent about my 'duini, I guess. I've never had one not work, even chinese cheapies. So I was trying out a new BBLeo (by Modern Devices, not a cheapie) and just assumed (oh dear) that it would work.

But there's something wrong with its i2c, not sure what yet; it will take a little time to figure out. Definitely flaky. When I swapped in a bog-standard Uno Genuino, all of a sudden I2C_Scanner started working reliably and presto, the OLED works too.

anyway my little blue OLED is now running through its demos happy as a clam. TTTT I'm not sure how useful a screen that tiny really is, but I couldn't resist them at the price!