Next.js Build failed because of webpack errors: CssSyntaxError

Question

I've been stuck and going all over internet trying to figure something that prevents my app to be build on Vercell (well locally as well).

• npm run dev - works great, no issues
• stylelint and eslint are cleaned up - no errors

The error comes from css-minimizer-plugin and is CssSyntaxError: Unknown word.

My question is - since it only shows location of the error inside static\css\363329e5478d19a3.css which gets immediately deleted when build fails - how on earth i can figure out what is the issue (what line of code in which file?)

Failed to compile.

HookWebpackError: localsitelocation\static\css\363329e5478d19a3.css:69:37: Unknown word
    at makeWebpackError (localsitelocation\node_modules\next\dist\compiled\webpack\bundle5.js:28:312635)
    at localsitelocation\node_modules\next\dist\compiled\webpack\bundle5.js:28:106060
    at eval (eval at create (localsitelocation\node_modules\next\dist\compiled\webpack\bundle5.js:13:28858), <anonymous>:44:1)
-- inner error --
CssSyntaxError: localsitelocation\static\css\363329e5478d19a3.css:69:37: Unknown word
    at Input.error (localsitelocation\node_modules\next\node_modules\postcss\lib\input.js:106:16)
    at ScssParser.unknownWord (localsitelocation\node_modules\next\node_modules\postcss\lib\parser.js:594:22)
    at ScssParser.decl (localsitelocation\node_modules\next\node_modules\postcss\lib\parser.js:237:16)
    at ScssParser.other (localsitelocation\node_modules\next\node_modules\postcss\lib\parser.js:434:12)
    at ScssParser.parse (localsitelocation\node_modules\next\node_modules\postcss\lib\parser.js:471:16)
    at scssParse (localsitelocation\node_modules\next\dist\compiled\postcss-scss\scss-syntax.js:1:322)
    at new LazyResult (localsitelocation\node_modules\next\node_modules\postcss\lib\lazy-result.js:133:16)
    at Processor.process (localsitelocation\node_modules\next\node_modules\postcss\lib\processor.js:53:14)
    at CssMinimizerPlugin.optimizeAsset (localsitelocation\node_modules\next\dist\build\webpack\plugins\css-minimizer-plugin.js:48:12)
    at localsitelocation\node_modules\next\dist\build\webpack\plugins\css-minimizer-plugin.js:79:55
caused by plugins in Compilation.hooks.processAssets
CssSyntaxError: localsitelocation\static\css\363329e5478d19a3.css:69:37: Unknown word
    at Input.error (localsitelocation\node_modules\next\node_modules\postcss\lib\input.js:106:16)
    at ScssParser.unknownWord (localsitelocation\node_modules\next\node_modules\postcss\lib\parser.js:594:22)
    at ScssParser.decl (localsitelocation\node_modules\next\node_modules\postcss\lib\parser.js:237:16)
    at ScssParser.other (localsitelocation\node_modules\next\node_modules\postcss\lib\parser.js:434:12)
    at ScssParser.parse (localsitelocation\node_modules\next\node_modules\postcss\lib\parser.js:471:16)
    at scssParse (localsitelocation\node_modules\next\dist\compiled\postcss-scss\scss-syntax.js:1:322)
    at new LazyResult (localsitelocation\node_modules\next\node_modules\postcss\lib\lazy-result.js:133:16)
    at Processor.process (localsitelocation\node_modules\next\node_modules\postcss\lib\processor.js:53:14)
    at CssMinimizerPlugin.optimizeAsset (localsitelocation\node_modules\next\dist\build\webpack\plugins\css-minimizer-plugin.js:48:12)        
    at localsitelocation\node_modules\next\dist\build\webpack\plugins\css-minimizer-plugin.js:79:55


> Build failed because of webpack errors