Portuguese has more distinct vowel sounds than Spanish, which means that for a Spanish speaker, two distinct words in Portuguese can sound the same. This makes

Portuguese has more distinct vowel sounds than Spanish, which means that for a Spanish speaker, two distinct words in Portuguese can sound the same. This makes it easier for a Portuguese speaker to understand Spanish, assuming the specific vocabulary is also similar enough. But it doesn't make for easy conversations when even one person is struggling to comprehend, as you've noticed.