No, it's not going to cost you another $100. Some basic tips...
Prior to starting a new project, go to OPTIONS | DISK tab and Clear Unused Cache Files.
Save Project File AS routinely, giving it a unique # or name, so as not to overwrite prior saves. Using Save Project Files (no AS) will overwrite. From the HOME tab, the AS choice is available by clicking the caret to the right of the Save Project button on the toolbar. That way you're protected, and shouldn't lose anything.
Use the 64-bit release. Here's one that should honor your license. It's from 5/25. Ignore any virus warnings.
Most of the clips in your screen grab are linked. If image clips are placed between them both their audio and video will be moved, possibly leaving a gap.
If these measures don't correct the issue, please share your project for analysis. That's THE best way to track down problems, which can result from a variety of factors. The process is not difficult. Just follow these steps one-by-one. Don't skip any...
Back up --- With your project on the timeline, click on MENU at the top-left. Click FILE|BACK UP PROJECT FILES TO FOLDER. Choose a folder and SELECT FOLDER.
Zip the folder --- It will be numbered. In Windows right-click on it and Send To > Compressed (zipped) folder.
Upload --- Use a free server - Google Drive, MS OneDrive, etc. - to upload the zipped folder. When it completes...
Get link --- Right-click the file and click SHARE. If using Google, right-click the file, click SHARE | SHARE. Change "restricted" to "anyone ... can view"
Share --- Click COPY LINK or OK | DONE. Paste that link here, or click the folder at the top-right of this forum to message it privately. It won't be shared.
And don't forget to change "restricted" to "anyone with link can view" if using Google Drive for the upload.