The playback and paused resolutions may have been changed. What version and operating system?
What are these snapshots?
What program are you using and on what computer operating system it is running on?
Previous reply to you in this thread assumed that you are working with Premiere Elements since this is the Premiere Elements Forum (video editing) where your thread is appearing. Any chance your program is Photoshop Elements? If your program is Photoshop Elements, please re-post your thread in the Adobe Photoshop Elements Forum or wait for a moderator to see your thread here and move it from here to there.
If you do have some version of Premiere Elements and this is a Premiere Elements question, please tell us which version and what computer operating system involved as asked. What is your project preset and are you looking at the rendered or unrendered Timeline in the Edit area monitor?
a. if you right click the Edit area monitor and select Playback Quality, do you get better results with the rendered image if you select Highest instead of Automatic for the setting.
b. what are the pixel dimensions of this snapshot and what is the format of this snapshot?
Let us start here and then decide what next based on your reply clarifying your program and situation.