Many websites encounter bugs after uploading new plugins from other sources due to compatibility issues, coding errors, or security vulnerabilities. Plugins from external sites might not be thoroughly tested or updated to work with your website's specific platform, theme, or other plugins. Additionally, these plugins could introduce malicious code or conflicts that disrupt site functionality. To avoid these issues, it's important to download plugins only from trusted sources, ensure they are compatible with your site's software version, and regularly update them. Always back up your site before installing new plugins to prevent potential disruptions.