Crystals.
Crystal
resonators are independent "discrete" parts, so they are cheaper and simpler but require the proper driver and capacitive loading to be in proper tune. You also have to buffer them if you want to drive very much, you can not load the leads of a bare crystal. Crystal resonators usually have only two pins/pads, though SAW filters are known to have 4 pins/pads.
Crystal
oscillators are the complete resonant circuit. Prebuilt modules generally exist to give something that works correctly out of the box, with little or no fiddling. Just power them within the right margins and they will output a digital friendly clock. They also have high drive current that lend well to driving large loads. These almost always have 4 pins/pads. It goes without saying, crystal oscillators obviously contain crystals.
Read this for more detailed info....
https://en.wikipedia.org/wiki/Crystal_oscillator (admitadly, the artical is not really pointing out differences).
In any case, plastic packaged crystal oscillators are not nearly as good as the hermetically sealed metal cased units IMHO. This is probably your problem with the SG531P. I'm fairly sure crystals don't like things touching them, and the plastic emulsifies the entire thing with those cases. I can easily see the crystal fracturing from very minor external forces, such as inserting them into a PCB. The can units usually have the actual crystal somewhat suspended in the case, and are 10X more likely to be temperature controlled goodness.
Lattice chips.
lattice semiconductor is a company that primarily makes CPLD's and FPGA's. These similar devices are somewhere between a microcontroller and a ASIC. They are fully programmable like microcontrollers, but they have repeating "fabric" of generic logic gates called "macrocells", and do not generally contain computer like blocks like a microcontroller. One generally use CPLD's and FPGA's when you either (1) are prototyping for something that is eventually going to be done almost entirely in printed silicon (hard coded). Or (2) you have a need for significant speed in a very particular problem set. You
CAN make full CPU's and other such complex things with these chips too, but it's not all that practical.
If the chips are single wide DIP's, then they are most probably just PAL compatible PLD's, the ancestor/forefather to the above chips.
https://en.wikipedia.org/wiki/Programmable_Array_Logic
My 2¢