Can anyone please explain why HashMap comparing it with another Hashmap is not working properly for large input of the string

Question

    class Solution {

    public boolean checkInclusion(String s1, String s2) {
    HashMap<Character, Integer> s1_map = new HashMap<>();
    HashMap<Character, Integer> s2_map = new HashMap<>();
    
    int s1_len = s1.length();
    int s2_len = s2.length();
    
    for(int i=0;i<s1_len;i++) {
        s1_map.put(s1.charAt(i), s1_map.getOrDefault(s1.charAt(i),0) +1);
    }
   
    int i=0;
    int j=0;
    
    while(j<s2_len) {
        if(j-i+1 <= s1_len) {
            s2_map.put(s2.charAt(j), s2_map.getOrDefault(s2.charAt(j),0) +1);
        }
        if(j-i+1 == s1_len) {
            if(isPermutation(s1_map, s2_map)) {
                return true;
            }
            
            s2_map.put(s2.charAt(i), s2_map.get(s2.charAt(i)) -1);
            if(s2_map.get(s2.charAt(i)) == 0) s2_map.remove(s2.charAt(i));
            i++;
        }
        j++;
    }
    
    
    return false;
}

public boolean isPermutation(HashMap<Character, Integer> s1_map, HashMap<Character, Integer> s2_map) {
    for(Character c : s2_map.keySet()) {
        
        if( s1_map.get(c) !=  s2_map.get(c)) { 
            return false;
        }
    }
    
    return true;
}}

The above code is the solution of LeetCode 567. Permutation in String. I used the sliding window technique to compare frequencies of the s1 in s2 using HapMap for both strings. The code is working for smaller inputs like

Input: s1 = "ab", s2 = "eidbaooo" Output: true Explanation: s2 contains one permutation of s1 ("ba").

but it is failing for the large input like this

But the strange thing is when we typecast s1_map.get(c) to (int)s1_map.get(c) and s2_map.get(c) to (int)s2_map.get(c) see below code for ref, the code is working fine for large inputs. Can anybody explain this strange behavior of hashmap?

public boolean isPermutation(HashMap<Character, Integer> s1_map, HashMap<Character, Integer> s2_map) {
    for(Character c : s2_map.keySet()) {
        
        if( (int)s1_map.get(c) !=  (int)s2_map.get(c)) { 
            return false;
        }
    }
    
    return true;
}