I've been using the ads8866 in a project, making an initial prototype on a perf-board that worked well (or as well as could be expected with the noise of wires dangling everywhere). Everything seemed to be working, so I moved it onto a PC board. Now using the same software (pinout, timing and everything) I initially soldered on an ADC and it didn't work at all. On the scope the DOUT pin started 3V and dropped to zero instantly and stayed there. I figured it may have been broken while installing, since I soldered it on by hand. Took the old one off, put on a new one with a little more care and got some data back this time. However, after closer inspection, I realized that the 3 least significant bits are always 0. The rest of the bits seem to be flipping with increasing load, just not the last 3.
Is this due to poor soldering technique, or could there be some other issue that can lead to missing bits? How fragile are these things to the heat of a soldering iron? Should we even attempt to solder these by hand?